wireless engineer - world radio history

WIRELESSENGINEERThe Journal of Radio Research & Progress

Vol. mx JUNE 1942

CONTENTSEDITORIAL. More Magnetic

Fallacies .. 239

SUPERHETERODYNE TRACK-ING CHARTS -1. By A. L.Green, Ph.D. .. 243

RESPONSE OF REACTIVENETWORKS TO FREQUENCY -MODULATED SIGNALS. ByJ. D. Weston 251

CORRESPONDENCE 253

WIRELESS PATENTS 257

ABSTRACTS AND REFERENCES 260-286

Published on the first of each monthSUBSCRIPTIONS (Home and Abroad)One Year 32 6 Months 16/ -

Telephone: Telegrams :Waterloo 3:333 (35 lines) Experiwyr Sedist London

No. 225

IJILIFFE & SONS LTD. DORSET HOUSE STAMFORD ST. LONDON S.E.1

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SALFORD ELECTRICAL INSTRUMENTS LTD.PEEL WORKS, SALFORD, 3. Telephones : BLAckfriars 6688 (6 lines). Telegrams and Cables : "Sparkless, Manchester"

PROPRIETORS: THE GENERAL ELECTRIC Co. LtA., OF ENGLAND

June, 1942 WIRELESSENGINEER

WE'RE UP TO OUR EARS, TOOLAUDE LYONS LIMITED has, up to the present, refrained from advertising the effectiveness of theirsupply of electrical and radio laboratory measurement equipment, electronic devices, meters, oscillo-

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graphs, voltage regulators (manual or automatic), receiving. and transmitting apparatus of ultra -highluality, components, hard -to -get high quality parts such as resistors, condensers, sockets, etc., etc. No, weRave accepted the greatly added strain upon our facilities, service department, etc., as a patriotic duty to theountry in which we plan and propose to be doing business for very many years to come. We have thereforeelt little inclination to burden the readers of " THE \VIRELESS ENGINEER " with an account of theagnitude of our present business. We have, also, consistently refused to waste the country's valuable[aper by absorbing the majority of our advertising space by pretty illustrations of Battleships afloat,irplanes in flight, A.A. Guns and Spotters on the job, etc. Such artistic efforts are wasteful of space whichian be devoted, and always has been devoted, by us to putting across essential information regarding theroducts we handle, in a form easily assimilable by the hard-pressed researchist or works engineer.3 Firms go, we are a small organisation. But we have back of us a formidable array of specialist manufacturingrganisations, most of whom we represent in the U.K. on an exclusive franchise basis. Great shortages have.xurred from time to time during the past few years of essential equipment, vital to the Electrical, Radiond "Electronics " Industries. We are proud to state that we have to a very large extent always been:ady and in a position promptly to fill those gaps. Furthermore we have, War or no War, introduced newad valuable additional measurement and/or testing apparatus almost every month. All persons and firmstouch with us have been kept advised by our normal monthly information letter and the distributionTaus) of such well known and widely appreciated house -organs as the " GENERAL RADIOXPERIMENTER " and the DuMont " OSCILLOGRAPHER," and we are hopeful of being able to continueese services in the or no War.

Representing (inter cilia)

GENERAL RADIO COMPANY, Cambridge " A," Mass., U.S.A.ALLEN B. DuMONT LABORATORIES INC., Passaic, New Jersey, U.S.A.

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SIMPSON ELECTRIC COMPANY, Chicago, Illinois, U.S.A.G.M. LABORATORIES INC., Chicago, Ill., U.S.A.

MONARCH MANUFACTURING CO., Chicago, Ill., U.S.A.CONTINENTAL CARBON OF CANADA, LTD., Toronto, Ont., Canada.

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THE HICKOK ELECTRICAL CO., INC., Cleveland, Ohio, U.S.A.and Many others

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,LE TO QUOTE TO ADVANTAGE AND TO INFLUENCE EARLY DELIVERIESTHE NECESSARY HIGH U.S.A. PRIORITIES.

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June, 1942

EIMAC 2501 25olVatis

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MaximumPlate Voltage ate

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'VETERANSof many outstanding

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4Past achievements

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bilitiesTheplates in Eitriac

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qi

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WIRELEENGINEER

Editor HUGH S. POCOCK, M.I.E.E. Technical Editor Prof. G. W. 0. HOWE, D.Sc., M.I.E.E,

VoL. XIX JUNE 1942 No. 225

EditorialMore Magnetic Fallacies

UNDER the title of " The Electro-magnetic Mental Picture " a letterwas published in Nature of Febru-

ary 28th in which H. Stafford Hatfielddiscusses the presentation to students of

engineering electricity " with specialreference to the teaching of radio telegraphy.He remarks that recent textbooks reflect acertain uneasiness, some teachers advocatingclassical field theory alone while othersintroduce the electron theory and link itup with the field theory at every stage.In an earlier letter to Nature (August i6th,1941) he had put forward a method ofexplaining the induction of e.m.f. in termsof the moving electrons without referenceto any magnetic field. He advocates basingthe consideration of capacitance, inductanceand transmission upon the " particle picture,"and says that " historical piety should notlead us to burden the beginner's mind withthe difficulties and artificialities of themagnetic field picture." While admittingthe usefulness of the field picture, he saysthat " the literature from the time ofFaraday to the present day affords numerousexamples of futile experiments and dis-cussions based upon a too literal interpre-tation of it." This is perfectly true, andwe need hardly remind our readers thatmany a sermon has been preached on thesame text.* We doubt, however, whetherthe average student or engineer is troubledby the pseudo -philosophic and usually

meaningless questionings which lead to thecarrying out of these futile experiments.We should hesitate to throw the magneticfield overboard after a century of usefulservice, simply because some people, whomistakenly endow the lines of force withconcrete reality, and regard them as bristlesor fibres which can be individually ear-marked and followed about, persist in askingmeaningless questions about their move-ment. The writer of the letter then givestwo cases in which he says that " the fieldpicture as usually stated seems to beinadequate " ; he is careful not to say thatit is inadequate, but only that it seems to be.When a person tells you that the room seemsto go round, you may be sure that there is ,

something wrong-but not necessarily withthe room. Let us look into these two cases." If a horseshoe magnet be rotated whenplaced so as to send flux through a fewturns only of a short-circuited toroid, thefield theory seems to call for an alternatingcurrent in the toroid, with no reactivetorque on the magnet." On the contrary,the field theory definitely rules out thepossibility of such a thing or even of placinga magnet so as to send flux through a fewturns only. The line integral of I/ around

* " A Perennial Chimera," G. W. 0. Howe, Electri-cian, 1934, pp. 329, 399. " A Persistent Fallacy,"G. W. 0. Howe, Electrician, 1936, pp. 191, 493." Magnets and Fields of Force," G. W. 0. Howe,Electrician, 1936, p. 625.

240 WIRELESSENGINEER

any closed path in the field of the magnetis zero. This applies to any of the dottedcircles in Fig. 1, hence E.01 = o where0 is the normal flux in the toroid at anycross-section. If there is a constant numberof turns per cm. it is immaterial whether0 be multiplied by the length 51 or by thenumber of turns -/8/ in this element of

length. Hence the total number of linkagesis zero whatever the position of the magnet

Fig. 1.

and no e.m.f. can be induced in the toroidby its rotation. To make this statementabsolutely correct the toroid should bewound with two layers of wire in series,in one of which the current follows a right-handed screw and in the other a left-handedscrew around the toroid, otherwise the wholewinding would act as a single short-circuitedturn through which flux would pass normalto the paper in Fig. i when the magnetwas turned. It is now evident that a magnetcannot be placed " so as to send flux througha few turns only," as the writer of the letterpremised-we suspect with his tongue in hischeek.

Torque

Turning now to the other case, we are toldthat " if a toroid solenoid is placed with itsplane at right -angles to that of a horseshoemagnet and with a few of its turns in thepole gap of the magnet, the field pictureseems to call for a torque on the toroid,but none on the magnet." Although hedoes not say so, the writer assumes that thetoroid is carrying a current.

From what we have seen in the first casethere can obviously be no torque since thereis no linkage, whatever the relative positionof the toroid and magnet. This case is,however, much more interesting and may

June, 1942

cause some readers a little trouble. Surely,they will say, the conductors carryingcurrent in the horizontal magnetic fieldof the magnet will experience a verticalforce, upwards on one side and downwardson the other, and thus exert a torque tendingto tilt the toroid. This is quite true, butyet the toroid does not tilt, and the magnetexperiences no torque. The field of themagnet outside the toroid cannot be affectedsince the toroid has no external field, henceno torque can be exerted on the magnet bythe current. The field of the magnet entersthe toroid symmetrically, but inside thetoroid it is compounded with the solenoidfield, which is therefore distorted as indicatedin Fig. 2. The force on the conductors isexactly that calculated from the field of themagnet and the current in the conductor,and the direction is that given by the left-hand rule, but the field picture shows that theforce is transmitted internally from oneside of the toroid to the other via the skewedmagnetic field. The toroid shows no moretendency to rotate than does a person whopulls steadily at his own braces.

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I

It requires no historical piety to admirethe beauty of this magnetic field picture.

There is another point mentioned in theletter. The writer says that he asked more

Fig. 2.'WI


than a dozen highly skilled physicists andradio research men whether the inductanceof a straight wire is greater or less than;that of the same wire bent into a circle,and that without exception they answeredwrongly. It is difficult to see how themagnetic field picture can be blamed for thislamentable state of affairs. It is probablethat the highly skilled persons had beenbrought up on an electron diet and weresuffering from a magnetic field deficiency.It would be interesting to know whatthe questioner himself understands by theinductance of a straight piece of wire.This subject was very much discussed inthe pages of the Elektrotechnische Zeitschriftabout thirty-five years ago, when a proposedset of definitions included one of the induct-'ance of a straight piece of wire. It was pointedout* that Neumann's approximate formula

L ---- 2l(loge -21 - 1 ± ), where p, is the per-' 4meability of the wire, is based -on an arbitraryand unjustifiable assumption, and that theinductance is really infinite. The wholething is fictitious because it assumes astraight piece of wire carrying a steadycurrent without any other conductors in the

i neighbourhood. If the wire concerned isAB in Fig. 3 and it be assumed ' to carryunit current-and no questions asked asto how the current gets in or out of the wire-the strength of the field at every point canbe calculated by the ordinary Biot-Savartformula, and on integrating throughout space,the total flux is found to be infinity. If,however, all the flux outside the two dottedplanes in Fig. 3 be excluded from theintegration, which, by the way, meansneglecting an infinite amount of flux, dueentirely to the current in the piece of wire,then the above fon-hula is obtained. Thismay, perhaps, be useful, but it is hardlycorrect to call it the self-inductance of thepiece of wire. Notwithstanding the above -mentioned discussion, this formula wasgiven in the Bulletin of the Bureau ofStandards, Vol. 8, No. i, 1916, p. 15o,without any comment ; an analogous formula

M --= 2/ [log -2/ - 1 + 11 was given for thed

* Guttsmann, 1905, pp. 764, 851, 936 ; Emde,1905, pp. 851, 935 ; also 1907, p. 185 ; Sumec, 1906,p.[1175 ; Wagner, 1907, pp. 673, 1002, 1132.

241

mutual inductance between two wiressituated as shown in Fig. 3 at a distance d.The definition given is interesting, viz.," the mutual inductance of two parallelwires of length 1, radius r and distanceapart d is the number of lines of force dueto unit current in one, which cut the other

when the. currentdisappears." Not, beit noted, when thecurrent is established,since that would raisesome awkward ques-tions, for the whole

D 7 of space is graduallyi d occupied by circularLI lines of force which

4A presumably originate

at the wire AB, andnot only expand ra-dially but move later-ally. How many ofthe infinite numberof lines of force which

Fig. 3. ultimately lie outsidethe pale cut the wire

CD in their movement ? Instead of at-tempting to answer this meaningless ques-tion, which would necessitate materialisingand ear -marking the lines so as to be able totrace their movements, the definition lets thecurrent die away and assumes arbitrarily thatthe lines of force all collapse radially ; thewire CD is then only cut by those betweenthe two dotted planes, and these are finite innumber and given by the above formula.Why, when the current decreases, the linesdo not exactly retrace the movement theymade when it increased, it is difficult to see.It should be carefully noted, however, thatall this-dare we say nonsense ?-is due notto any magnetic field picture, but to theattempt to define something which isphysically impossible and inconceivable.

Self -Inductance of a Solenoid

What do we mean when we speak ofthe self-inductance of a. solenoid ? If anisolated straight piece of wire has an infiniteinductance,' the same must be true, onlymore so-of a solenoid between the sametwo terminal points. Here again we cannotassume a steady current in the coil apartfrom the remainder of the circuit without


doing violence to any intelligent conceptionof nature. By the inductance of a solenoidwe must understand the increase in theinductance of a circuit when the solenoidreplaces a straight piece of wire betweenthe same terminals.

June, 1942

We see, therefore, that the problempropounded to the highly skilled physicistsand radio research men was not nearly sosimple as it sounded, but involved thecomparison of a finite real quantity with aninfinite imaginary one. G. W. O. H.

Pulsatance, Rotatance or Velocitance ?IF one, why not the others ? " Pulsatance "

was proposed many years ago and hasbeen used to some extent as a name for

the angular velocity of the vector repre-senting an alternating voltage or current,but surely it is a very inappropriate name.The word " pulse " conveys a very definiteidea. The dictionary gives " pulsate, tobeat, as the heart or a vein ; to throb " ; also" pulsation, a beating or throbbing ; anymeasured beat ; a vibration." Now, ifanyone could see, feel, or hear the variationsof an alternating current or voltage, theywould have no doubt about the suitabilityof the word " pulsation " to describe thephenomenon, and if asked to count the pulse,their only doubt would be whether a com-plete cycle should be counted as one oras two pulses. If superposed upon a steadycurrent, even this doubt would be unlikelyto arise. Surely, then, " pulsatance," ifused at all, should signify what is univer-sally called the frequency.

The alternating current or voltage can berepresented by the projection on the verticalof a rotating line usually called-to theannoyance of mathematical purists-a vector.This line must rotate f times per second, andtherefore its angular velocity w is 27Tfradians per second. There is nothing what-ever pulsating about this angular rotation ;there are 27T radians in each revolution, butcertainly not 217 pulses. Why, then, referto this, steady angular velocity as the pulsa-tion or pulsatance ? Someone may suggestthat the pulsatance is the number of pulsesin 27T seconds, just as the frequency is thenumber in one second, but this is not thesense in which the word is used, for it isalways given as so many radians per second.Many people avoid its use by referring to afrequency of 1,000/27r cycles per secondrather than a pulsatance of L000 radiansper second. Surely either " rotatance " or

velocitance," strange though they maysound, are preferable to " pulsatance " as aname for, or associated with, a rate of steadyrotation. One would soon become accus-tomed to speaking of an alternating currentwith a rotatance of Loa) radians per second.It is certainly more suggestive of what itrepresents than a pulsatance of L000 radiansper second. The difficulty is that while thereis nothing pulsational about the rotatingvector, there is also nothing rotational aboutthe alternating current, and consequentlyany term used to link them is almost boundto consort badly with one or the other.What is required is really an abbreviation ofvector -angular -velocity, but we cannot thinkofalthough " radiance " struck us as a brightidea. It would be interesting to know theviews of our readers on the matter.

G. W. O. H.

Meeting a NeedREADERS who in the past have been

accustomed to consulting foreign tech-nical journals at libraries, or sub-

scribing to them direct, have been unableto do so as a result of the war. Our Abstractsand References section is often the onlyremaining guide to them as to what is beingpublished abroad. As a result of requests,and in order to help remedy this state ofaffairs, it is proposed to publish translationsof foreign papers of special interest andoccasionally to reprint from journals printedin English \there the journals are notgenerally available in this country.

This arrangement is being introduced withthe publication in this issue of an article byDr. A. L. Green entitled " SuperheterodyneTracking Charts," which appeared in No. 3,Vol. 5, of the A.W.A. Technical Review.

e;;


Superheterodyne Tracking Charts-I*By A. L. Green, Ph.D.

ABSTRACT.-It is well known that the formulae customarily used for the calculationof padding and trimming condensers in the oscillator section of a superheterodyne receiverare cumbersome and susceptible to arithmetical error. This report introduces formulae,suitable for slide -rule computations, that arise out of simple modifications of the early two-p`bint tracking analysis. The modifications include a certain correction factor (k), for whichnumerical values are given in the form of charts.

1. Historical Summary.IT was recognised at an early stage in the

development of the commercial super-, heterodyne receiver, that ease of operationdemands the inclusion of a uni-controltuning mechanism. As is now well known,the design problems associated with thisdesirable feature are incurred in the re-quirement that the oscillator tuning musttrack with the signal -circuit tuning. Moreprecisely, it is necessary that the differencebetween the frequencies of the signal andoscillator circuits be a constant quantity,equal to the intermediate frequency of thereceiver, independently of the setting of thetuning dial.

In an early experimental receiver, Chinn(1931).1. secured effective tracking of thesignal and oscillator circuits by shuntingan adjustable trimming condenser acrossthe signal circuit, thus reducing the fre-quency ratio of this circuit in comparisonwith the oscillator. In this receiver theoscillator frequency was always lower thanthat of the signal circuit. At about thesame time, Andrewes (1931) described theuse of both a parallel trimming condenserand a series padding condenser in theoscillator circuit, for the purpose of reducingthe frequency ratio of the oscillator circuit.In the same year, Haynes and Cocking (1931)claimed to have produced the first solutionto the problem of securing correct trackingin a receiver that included both medium -wave and long -wave ranges. Briefly, themethod provided a series padder in theoscillator circuit, the same condenser beingused on both wave ranges, and independentparallel oscillator trimmers for the twobands.

* Reprinted from A .W .A. Technical Review, 1941,Vol. 5, No. 3, by arrangement with AmalgamatedWireless (Australasia) Ltd.

t See chronological bibliography at end of article.

243

The generally accepted solution to thesuperheterodyne tracking problem was givenby Sowerby, in 1932, in an article whichdescribed clearly the idea of three-pointtracking and the fact that the values of boththe oscillator padder and trimmer areuniquely determined by this criterion.Briefly, it was shown that the earlier designswere subject to serious tracking errors to-wards the centre of a band in which correctalignment had been secured at the twoextreme tuning points. In Sowerby's three-point tracking, correct alignment was alsoachieved at a third tuning point, whichcould conveniently be specified as thearithmetic -mean frequency of the band.This article has remained the authorityon the superheterodyne problem until thepresent day, although somewhat similarresults have been obtained by otherauthors, including Landon and Sveen (1932),Kautter (1935), Roder (1935), Singer (1936)and Couppez (1936). A more ambitiousfour -point tracking scheme has been de-scribed by Lange (1937), but in this case theoscillator circuit includes a two -sectionganged tuning condenser.

A useful result of considerable practicalimportance was derived in 1937 by Cocking,who presented the case for padding con-densers of fixed values, thus eliminating theearlier adjustable padder. Cocking demon-strated that an easily obtained manu-facturing tolerance in padder capacity wasquite sufficient for satisfactory three-pointtracking. In the same year, however,Sklar had described an automaticallyadjusted padding condenser to give anapproach to perfect tracking at all tuningpoints in the band, in place of the customarythree-point tracking. This method requiresthe use of a small variable condenser,shunted across a fixed padder and gangedwith the main tuning condenser.


More recent articles have discussed theproblem -of three-point tracking from thepoint of view of using outer tracking pointswhich differ somewhat from the extremelimits of the band. It has been shown byCocking (1938), in " Electron Art " (1939),and by Wald (1940), that this refinementreduces the maximum tracking error.

Although the present paper is concernedwith the problem of three-point tracking,it is important to remember that an alterna-tive scheme is available for use in receiversthat include only one wave -band. Thismethod requires the use of a speciallyshaped oscillator section of the gangedtuning condenser, and of prior knowledgeof the stray minimum capacitances in thesignal and oscillator circuits. Mathematicaltreatments have been given by Schwartz-mann and Burnell (1934), and by Schad(1935), and it was pointed out that it isstill necessary to add padding condensers,and to rely on Sowerby's analysis, if thetuning range is extended to more than theone band for which the tuning condenser hasbeen designed.

2. Two -point Tracking.

In superheterodyne design problems it isfrequently necessary to estimate the valuesof the oscillator padding and trimmingcondensers, in order to obtain an approximatevalue of the oscillator inductance. Unfor-tunately, however, it is by no means a simplematter to compute values of these two com-ponents from the Sowerby formulae. Ingeneral, it appears to be easier to use theelementary two -point tracking formulae,for the purpose of estimating very approxi-mate values of the components in theoscillator circuit, and to rely on a moreprecise evaluation by experiment at a laterstage. It is known, empirically, that thisprocedure gives satisfactory results for ashort-wave band, i.e., one in which thesignal frequency is far removed from theintermediate frequency of the receiver.On the other hand it is also a matter ofexperience that the two -point trackinganalysis is inadequate for medium -frequencyand low -frequency bands, i.e. bands inwhich the mean signal frequency is com-parable with or lower than the intermediatefrequency.

Thebriefly

L,C,

June, 1942

two -point tracking formulae maybe stated as follows :-col = low -frequency tracking point

of the signal circuit,0)2 = high -frequency tracking point

of the signal circuit,intermediate frequency,

= co 2/co = signal frequency ratio,p =W2 ± Wi = oscillator - frequency

w 1 ± wi ratio,Lo =signal and oscillator inductances,Co = signal and oscillator trimming

capacitances,C = padding capacitance,Cg = added capacitance of each sec-

tion of the ganged tuningcondensers.

The circuits assumed to be used areindicated in Fig. 1, and it is particularly tobe noted that the trimming capacitances Cand Co include, not only the customary andfixed portions of the trimmers, but alsoallowances for the minimum capacitance ofthe ganged tuning condenser, input andoutput valve capacitances and all strays.In the formulae all frequencies are in angularmeasure.

Wi =

9

Fig. I.-Skeleton circuits on which the analysisis based.

The four equations for two -point trackingare obviously :-

L (Cg C) W 12 = 1 (I)LCui22 =1 (z)

1Lo(wi = -+Cu+Co (3)

Lo (cot w2)2 =C2,± (4)

The quotient of expressions (I) and (2)immediately gives the value of the signal-circuit trimmer as

=a2 Cg (5)

ti


and the signal -circuit inductance is thenreadily derived from tables of LC products,for example Hesse (1938).

It is clearly impossible to solve equations(3) and (4) for unique values of L0, CO, andC, unless a value is first assigned arbitrarilyto one of the three variables. In practiceit is usual to make the assumption that

Co C (6)

and it is then easy to show, with the helpof expression '(5) above, that the value ofthe padder in two -point tracking is

C92 =/3

2 P2 (Cg C) 'GC - p (7)

With C and C0 known, it is again a simplematter to calculate the corresponding in-ductance.

In general, therefore, expressions (5),(6) and (7) have customarily been used in thecalculation of approximate values of circuitconstants in superheterodyne tracking pro-blems, in spite of their known inaccuracy.

3. Three-point Tracking.In order to reduce tracking errors towards

the mid -point of a band, Sowerby has shownthat the receiver may be aligned at a thirdtracking point which, for convenience, maybe the arithmetic -mean frequency of theband to be covered. We therefore define

(03 =W1+

W2 arithmetic - mean signal2 tracking frequency,

C3 = added capacitance of each sectionof the ganged tuning condenserat the tracking frequency,

= corresponding oscillator trackingfrequency.

Corresponding with the four LC equations(I), (2), (3) and (4) for two -point tracking,there are two additional expressions for thethird tracking point as under :-

L(C3 C)(.032 = I (8)

Lo(CO3 + Wi)2 =- +Cy C3 + Co

and it is also convenient to introduce afurther frequency ratio (8), which defines theproximity of the band to the intermediatefrequency of the receiver, i.e.,

cug8 =

I

co3

(9)

(ro)

245

Trininiers.---The method of attack is tofollow the two -point tracking solution byfirst solving equations (1) and (2) to obtain

C

as before. Next, eliminate L0 and C be-tween equations (3), (4) and (9), leaving anexpression containing only the two unknownquantities C3 and CO. The quantity C3 isreadily found in terms of C from equations(2) and (8), by eliminating L, and then it isonly necessary to remove C3 from the twoderived expressions in order to find C0 interms of the known C. This procedure, withthe help of (5), leads to the followingsolution :

C,

Cu)C0 = (rra(1 -k)2

in which the new symbol (k) is, in effect, acorrection factor which differentiates be-tween two -point and three-point tracking.The correction factor has the form,

46 (0:2 - I)k= (i + 3a) . {3 a + 28 (r oc)}(12)

(/32 - r) (Cg C0)C =-- . (13)(I - k) a2 -

which demonstrates a remarkable similaritywith the previously derived two -point paddervalue,

C2= p2

Corresponding exactly with the previousdiscussion on C0 in short-wave bands, C,obviously approaches closely to the two -

(5)

from which it is immediately apparent thatthe amount of correction is negligible forshort-wave bands in which 8 is obviously asmall quantity. For such bands expression(II) reduces very simply to

C, -> g C . (lib)-which is, of course, the customary assump-tion, (6), made in the two -point trackinganalysis.

Padder.-As to the three-point paddervalue, it is only necessary to eliminate L0between equations (3) and (4), thus relatingC, to CO, C,, and /3. .The solution for C, isthen, with the help of expressions (5) and(Ira),

(12 - I) (Cr, + C)(7)


point padder value when the correctionfactor becomes small, that is to say when 8is a small quantity. On the other hand, forlong -wave bands in which 8 is actuallygreater than unity, k becomes a large frac-tion and it is no longer permissible to use thetwo -point formulae without the correctionfactor.

The Two -point -Tracking Assumption.-Inthe preceding section it was pointed outthat the two -point LC equations are in-soluble, unless an arbitrary value is assignedto one of the variables. At first sight itwould appear to be a safe assumption that

Co -'C . . . . (6)

that is to say, safe from the point of view ofcomputing a value of the padding condenserthat is close to the desired three-point value.Experience shows, however, that this is byno means the case, and it is therefore to beinferred that the assumption expressed in(6) is untenable. The degree of inequalitybetween C and Co is readily seen in the com-parison of expressions (5) and (11a), whosecombination gives

C k oc2= ICo oc - I

It is interesting to notice that the trimmerratio is independent of the size of the variabletuning capacitance and also that, on accountof the presence of the correction factor k,

0.40

0-38

0.36

0.34

032

0.300

0-28a0 0 26

0 24

0.22

SIGNAL -FREQUENCYRATIO (GO -3.5

3.0

0.24

0'22

0.20

0.18

0.16

0'14

0.12

0.10

0 08

006

(iLl)

June, 1942

the trimmer ratio obviously tends to unityas the mean frequency of the band is in-creased.

The ratio of the signal and oscillatortrimmers is a quantity of some practicalimportance in a multi -band receiver, be-cause it may be desired to use a commonoscillator trimmer for a plurality of bands,and thereby to reduce the number of com-ponents in the tuning unit. In such cases,the maintenance of a constant signal -frequency ratio for all bands immediatelyequalises the capacitances of the signal -circuit trimmers, and the possibility ofextending the principle to the oscillatorcircuits may then be gauged from expression(14) above. Numerical values of the trimmerratio are illustrated in Figs. 5, 6 and 7, withrespect to the parameter 8.

Arbitrary Tracking Points.-The refine-ment, described by Cocking (1938), thatconsists in using arbitrarily chosen alignmentfrequencies, rather than the outer limits ofthe band, may readily be introduced intothe foregoing formulae. A practical modifica-tion may be achieved by continuing to usethe symbols w1 and (v2 to denote the outertracking points, and by introducing thesymbols w'1 and w'2, respectively, for theextreme low -frequency and high -frequencylimits of the band to be covered. Corre-spondingly we define

3.0

2.5

0.055

0'050

0 045

0 040

0-035

0-030

0.025

0 020

0015

0010

3.5

3.0

2.5

2.0

0 2 %2 4 6 8 10 12 0.040 0 2 0 4 0 6 0'8 I 0 I 2 0'0050 0.02 0.04 0.06 0.08 0.10 0.12

RATIO (6) OF INTERMEDIATE FREOUENCY TO TRACKING FREQUENCY

Fig. 2. Correction factor chart Fig. 3. Correction -factor chart Fig. 4. Correction factor chartfor low frequency bands. for medium -frequency bands. for high frequency bands.

a) 2= = signal -frequency ratio for the1 whole band,

C'0 -- added capacitance of each sectionof the ganged tuning condensers,required to tune the signal circuitbetween w'1 and co'2.

C', C'0 = signal and oscillator trimmingcapacitances, corresponding withthe frequencies (0'2 and 0;2 wi.

June, 1942 WIRELESS 247ENGINEER

in which w'2 > w2and 0/1 < c°1-

The value of the trimming capacitance forthe full band is readily derived from (r5)and (i6), and is

C' oc,2 I

In order to evaluate CO, we have, from (2)and (i6), that

a'

180

175

170

165

160

155

150

145

140

135

1300

SIGNAL FREQUENCYRATIO (a) =3-5

3-0

2.5

2.0

2 4 6 8

RATIO (8) OF INTERMEDIATE FREQUENCY TO TRACKING FREQUENCY

Fig. 5. Trimmer -ratio chartfor low frequency bands.

(I7)

140

136

132

128

124

120

116

112

108

104

1000

110

109

108

107

106

105

104

103

102

101

1000

3 5

3.0

2.5

3.5

2.03

2.5

2-0

02 04 06'08 10 12 0-02 0.04 0.06 0-08 0.10 012

Fig. 6. Trimmer -ratio chart Fig. 7. Trimmer -ratio chartfor medium -frequency bands. for high frequency bands.

It is to be noted that the quantities Cand Co still represent the minimum capacit-ance in each circuit at the high -frequencytracking point, so that each of these symbolsnow contains a component that is a portionof the variable tuning capacitance.

Usually the value of C', is known, sinceit is the total variation in capacitance of thetuning condenser. On the other hand, ifthe tracking points are defined in terns ofthe tracking frequencies 0)1 and co2, and notin terms of the corresponding capacitancevalues of the tuning condenser, it is thennecessary to calculate the appropriate valueof C, for use in the formulae. For thispurpose we have, for the signal circuit,

L(C' C')(1)' = (15)L(C C)w12 = (I)

LCw22 = I (2)LC'co'22 = (16)

C212

=and, from (1) and (2), that

C -OC

2Cg (5)

The combination of (5), (17) and (i8) thenimmediately gives the desired relation be-tween C, and C'0, that is to say

C99

(co,W2

,

2. (oc,2cx2

(i8)

Having made the preliminary calculation ofCO, knowing C'0 and the relevant frequencies,it is then possible to proceed with the com-putation of the remainder of the componentvalues exactly as specified in precedingsections. In brief, Cocking's refinement isintroduced by defining a new value of C0that corresponds, not with the extremefrequency coverage of the band, but with


the coverage between the specified trackingfrequencies.

Finally it is to be noted that the differencebetween the calculated values of C and C'obviously represents the variation in tuningcapacitance between the high -frequency limitof the band and the high -frequency trackingpoint. This quantity is readily derived from(5) and (i7), after C9 has been computed,and is then available when it is desired toconvert the calculated value of Co into themore useful C'o.

4. Summary and Numerical Examples.The formulae required for the computa-

tion of C, Co and C9 are summarised here forconvenience :-

a = ratio of signal frequencies of theouter tracking points,

p = corresponding ratio of oscillatorfrequencies,

8 = ratio of intermediate frequency tothe arithmetic -mean signal -track-ing -frequency,

C9 = capacitance variation of each sectionof the ganged tuning condenser,between the outer tracking points,

C = capacitance of oscillator series -padding -condenser,

C, Co = capacitance of signal and oscillatortrimmers at the high -frequencytracking point ; the symbols in-clude the customary fixed andvariable portions of the trimmers,the minimum capacitance of thetuning condenser, all stray shuntcapacitances, and, in the case ofarbitrarily chosen tracking points,allowances for the added capacit-ance of the variable tuning con-denser at the high -frequencytracking point,

k = three - point - tracking correctionfactor,

C'9 = total capacitance vanation of eachsection of the ganged tuningcondenser, when this quantitydiffers from C9 above,

C',C'0= capacitance of signal and oscillatortrimmers at the high -frequencylimit of the band, when this fre-quency differs from the high -frequency tracking point, and

June, 1942

a' = ratio of signal frequencies of theextreme limits of the band, whenthese frequencies differ from theouter tracking frequencies.

(.02, 0)/2= respectively the high - frequencytracking point and the high -frequency limit of the band.

CC9

co (I - k)a2 - Ip( 2 - 1) (c, ± co)

(I - k)c(2 - P2where

48(a0 I)k = (12)

300{3 + a + 28(1 + a)}The factor k has been evaluated and plotted

in Figs. 2, 3 and 4, for selected values of thesignal -frequency ratio. As to Co, it is some-times more convenient to use the formula,

C k(Id)

values for which have been plotted in Figs.5, 6 and 7.

When the outer tracking points are arbi-trarily chosen in terms of frequency, it isnecessary to calculate the correspondingvalue of the tuning capacitance variation,C9, from a knowledge of the total capacitancevariation, C'9. For this purpose we havethat,

(012

C'9 (A)2 ) \a'2 - 1)and it is also useful to remember that

= /(-ct2)2C' (02

when it is desired to correlate the signal fre-quency with the tuning capacitance, at thehigh -frequency tracking point.

(19)

(18)

Example I. Broadcast Band with ExtremeTracking Points

Total frequencykc/s.

Outer tracking1,700 kc/s.

Arithmetic -mean1,120 kc/s.

coverage = 540 - 1,70o

frequencies = 54o and

tracking frequency


Intermediate frequency = 455 kc/s. Intermediate frequency = 455 kc/s.8 455 - 0.406, 8 455 = 0.4136,

1,120 1,100

1,7003.15,

1,500a = = 2.143,cc -540 700

C42 = 9.9,1,700 + 455

2.165,540 + 455

P2 = 4-69.The value of the correction factor (k) may

be derived from the chart in Fig. 3, byinterpolating between the curves respectivelyfor a = 3 and a = 3.5, or calculated withgreater accuracy from expression (12), whichgives

k = 0.1455.

The value of C is calculated from expres-sion (5), assuming that C9 = 42o jai/F., and is

420C -= 47 µµF.9.9 -

The value of Co may be derived from thechart in Fig. 6, by interpolating between thecurves respectively for a = 3 and a = 3.5,or calculated with greater accuracy fromexpression (hia), which gives

42°Co = - 56 µµF,(1- 0.1455) 9.9 I

showing that Co is greater than C by 9 AuF.Finally, for the value of the three-point

padder, we have from expression (13) that

(4.69 - I) (42o + 56)C- = = 466 µµF,,(I - 0.1455) 9.9 - 4.69whereas the two -point tracking formula,expression (7), gives a much smaller paddervalue of

(4.69 - I) (420 + 47)C = 330 F.9.9 -

Example 1L-Broadcast Band with ArbitraryTracking Points

Total frequency coverage = 540 - 1,700kc/s.

Arbitrary tracking frequencies = 700 and1,500 kc/s.

Arithmetic -mean tracking frequency =1,100 kc/s.

C, - (1 - 0.103) 4.593 - 2.865= 426 p.t.cF, from (i3).

On comparing these values with thosepreviously derived in Example I, for thesame frequency band, it is to be rememberedthat C and Co now contain components dueto the movement of the tuning condenserfrom the extreme high -frequency point(1,70o kc/s) to the outer tracking point(1,500 kc/s). This difference is clearly13 iuiciF, for both signal and oscillator circuits,since the constants of the signal circuit mustbe the same in Example II as in Example I,and the variable condensers used in the signaland oscillator circuits are identical.

C(2 = 4.593,1,500 + 455700 + 455

P2 = 2.865.

= 1.693,

249

It is first necessary to calculate Co.,knowing that C'9 = 420 We have that

, 1,700cc =540

= 3.15,

(4,2 = 9.9,(1,700)2 (4.593 - I)

420 = 217 pliF,i,500 (9.9- I)

from expression (19). The remainder of thecalculations follows along lines similar tothose in Example I.

k = 0.103, from the chart or from (1-217C = = 6o µµF, from (5).

4.593 -ICo (1 - 0.103) 4.593 -

= 69 icti.LF, from (hia).

(2.865 - 1) (217 + 69)

217

Example III.-Short-Wave BandTotal frequency coverage = 7.67 - 23

Mc/s (13 - 39 metres).Outer tracking frequencies = 7.67 and

23 Mc/s.


Arithmetic -mean tracking frequency =15.33 Mc, s.

Intermediate frequency = 455 kcis.0.455 = 0.0297.15.33

=23 + 0.455

fl 7.07 0.455

k = 0.0155, from Fig. 4 or expression (12)420C = = 52.5 from (5)9-I

Co (1 - 0.0155) 9 -1= 53.5 /.1.0F, from (Ira).

(8.34 - I) (420 + 53.5)C. = = 6,800 µ,µF ,- 0.0155) 9 - 8.34

from the three-point formula (13), whereasthe two -point -tracking padder value is,from (7),

420

2.89 ; f32 = 8-34-

(8.34 - I) (420 + 52.5)Cp2 = 5,250 pliF.

9 - 8.34It is therefore apparent that, although thevalues of the signal and oscillator trimmersare very nearly equal, as was to be expected,there remains an appreciable difference be-tween the two -point and three-point paddervalues. Finally it is to be noted that themost likely source of arithmetical error is inthe denominator of expression (13) for thepadder, in which occurs the difference be-tween two nearly equal quantities. Caretaken with this portion of the computationswill clearly allow the remainder to be doneon a slide -rule.

BIBLIOGRAPHY.

1931. Chinn, H. A. : " A High -frequency Converterwith Single -dial Control." QST, Vol. 15,No. 6, p. 9.

Andrewes, H.: " Single Control Superhetero-dynes." Tireless World, Vol. 29, p. bib.

Haynes, F. H. and Cocking, W. T. : " Single -Dial Superheterodyne." Wireless World,Vol. 29, p. 654.

1932. Sowerby, A. L. M. : " Ganging the TuningControls of a Superheterodyne Receiver."Wireless Engineer, Vol. 9, p. 7o.

McNamee, B. F.: " The Padding Condenser."Electronics, Vol. 4, p. 16o.

Landon, V. D. and Sveen, E. A. : " A Solutionof the Superheterodyne Tracking Problem."Electronics, Vol. 5, p. 25o.

June, 1942

1934. Martin, L. : " Tracking Problems in All -

Wave Superheterodynes." Radio E ngi nee -

ing, Vol. 14, No. o, p.Schwartzmann, H. and Burnell, L. G.: " De-

sign of Superheterodyne Tuning Condenser.Electronics, Vol. 7, p.

1935. Kautter, \W.: " Calculations for Super-heterodyne Receiver Alignment." Elect.Na,ch. Techn., Vol. 12, p. 31.

Schad, Dr. : " Design and Calculation ofGanged Condensers giving a ConstantFrequency -Difference." Funk. Tech.11onats-hejte, No. 4, p. 155.

Roder, H. : " Oscillator Padding." RadwEngineering, Vol. 15, No. 3, p. 7.

1936. Singer, C. P. : " Ganging a Superhet."Wireless Engineer, Vol. 13, p. 307.

Couppez, R. C. : " Uni-Controlled Super -heterodynes.'' ' L'Onde Elect., Vol. 15,

p. 804.1937. Lehmann, : " Note on the Alignment 01

Uni - Controlled Superheterodyne Re-ceivers." L'Onde Elect., Vol. 16, p. 132.

Lange, J.: " Improvement of the Alignmentin Superheterodyne Receivers.'' F14nk,Tech, Monatshelte, No. 4, p. 113.

Cocking, \V. : " Superheterodyne PaddingCapacities." 11'ireless Engineer, Vol, 14,

P. 246.Sklar, L. B. : " The Padding Condenser.

Electronics, Vol, 10, No. 5, p. 40.1938. Cocking, W. T. : " Wireless Servicing

Manual " (Appendix 1, SuperheterodyneGanging) , 4th Edition, Iliffe and Sons,Ltd., London.

Hesse, H. R.: " Six -Place L.C. ProductTable." Electronics, Vol. 1i, No. 6, P. 30.

1939. Electron Art : " Design of Oscillator Circuitfor Superheterodyne Receivers." Elec-tronics, Vol. 12, No. 1, p. 46.

1940. Wald, M. : " Ganging Superheterodyne Re-ceivers." Wireless Engineer, Vol. 17, p. 105.

Conserving Paper SuppliesThe urgent demands upon shipping space com-

pel the Ministry of Supply continuously to drawthe attention of the public to the necessity forsalvaging waste paper and conserving the supplyof new paper. Statistics show that a large per-centage of letters are still enclosed in new envelopes ;and we are reminded that care in opening envelopesis essential to ensure their re -use.

GOODS FOR EXPORTThe fact that goods made of raw ma-terials in short supply owing to warconditions are advertised in this journalshould not be taken as an indicationthat they are necessarily available for

export.


Response of Reactive Networks toFrequency -Modulated Signals *

By J. D. Weston

APROBLEM which arises in the theoryof modulation is that of determiningthe distortion which a modulated

signal undergoes in transmission through asystem of linear reactive circuits. Thatsome distortion must occur is obvious, inanything but an ideal network. For designand other purposes, it is necessary to havesome knowledge of the general nature of theeffects produced in practical networks bythe modulation of a sine wave.

One is familiar with the requirements ofa system intended to transmit amplitudemodulated signals. The case of frequencyor phase modulation seems to be less clearlyunderstood. In either case, it is possibleto approach the problem by way of thetheory of sidebands, in which considerationis given to the spectral distribution of thesignal energy. By this method it is possible,knowing the steady-state frequency responseof a network, to estimate the relationbetween the output spectrum and the inputspectrum. In the case of amplitude modula-tion, this result is easily interpreted in termsof the effect on the modulation envelope.For example, symmetrical attenuation ofthe sideband components farthest from thecarrier is equivalent to a relative loss ofhigh modulation frequencies. In the caseof frequency modulation, however, thesideband distribution is not so simple and,when the deviation ratio is large, manypairs of sidebands are of importance andthe effect on the modulation of relativelyattenuating some of them is not so easilyperceived. It behoves us, therefore, toconsider an alternative way of viewing theproblem, appealing more directly to thephysical mechanism involved, and per-mitting a readier visualisation of the prin-cipal effects of a varying frequency.

Let us consider the response characteristicof a simple tuned circuit, shown diagram-

* MS. accepted by the Editor, February, 1942.

251

matically in Fig. I. This may be referredto as the steady-state characteristic, for itindicates the response to a pure sine waveof any frequency, f, provided that this wavehas been applied for a sufficiently long timeto allow the transient oscillation, which isinitiated by switching on, to decay to anegligible amplitude, due to the dampingof the circuit. If either the amplitude orthe frequency of the wave is now changed,the circuit does not immediately respond tothe change. A transient oscillation takesplace, "at the natural frequency of the system,and decays logarithmically at a rate de-pendent upon the decay factor of the circuit.

1200

so°

40°

0

- 40°

-130°

V

AMPLITUDE

PHASE

FREQUENCY

Fig. 1.

When a wave to which the circuit is tunedis subjected to amplitude modulation, thistransient effect is in such a phase that ittends to counteract rapid changes in theamplitude of the signal. Thus, if the periodictime of the modulation is short in comparisonwith the time of decay for the circuit, themodulation will be attenuated. This isanother way of looking at the phenomenonof sideband cutting.


If the frequency of the applied signal ischanged quickly, the circuit will not respondin accordance with Fig. 1, owing to theaddition of the transient. The effect ofthis transient may be examined as follows.Let two waves, sin cot and k sin (w + p)t ,be superimposed on each other. k is therelative amplitude of the smaller signal.We have

sin cot k sin (w + p)t=_ (1 + k cos pt) sin wt k sin pt.

cos cot,

= a(cos b. sin wt + sin b. cos wt)= a sin (cot b),

where a2 = (r k cos pt)2 k2 sine pt= k2 + 2k cos pt,

and tan b = k sin ptk cos pt

That is, the sum of the two waves may bewritten as

k2 + 2k cos poi sin

{cot ± arc tank sin pt)

k cos pt )1

This shows that, when two pure sine wavesof different frequencies are added together,the resultant is a wave which is modulatedin both phase and amplitude. When k ismuch less than unity, the wave becomes,approximately,

(1 k cos pt) sin (ad k sin pt)This represents amplitude and phase modula-tion at the difference frequency, the fre-quency excursion being kp.

Now, in the case of interference by atransient, caused by a sudden change offrequency, the factor k in the above formulaebecomes e-vt , where y is the decay factorof the tuned circuit, and t is the time,measured from the instant when the fre-quency was suddenly changed from (cu P)

27r

the natural frequency, to - . Thus, super-

imposed upon the impressed change offrequency, there is an evanescent oscillatorychange. The importance of this effect canbe reduced by making y large, i.e., by heavilydamping the circuit. If the frequency ischanged more or less gradually, by amodulating signal, the transient effect or" sluggishness " of the circuit, still gives

June, 1942

rise to spurious frequency modulation, i.e.,distortion is introduced. The effect of theamplitude modulation at the beat frequencyis unimportant because, in a frequencymodulation receiver, it is eventually re-moved by the limiter.

It is now clear that, to obtain the responseof a tuned circuit to a varying frequency,it is not necessarily sufficient to assumethat impedance formulae which are knownto be valid for a steady frequency are alsovalid when the frequency is replaced, in theformulae, by a varying frequency. How-ever, physical intuition makes it obviousthat, if the frequency variation is slowenough, and if the rate of change of responsewith respect to frequency is not too great,approximately true results can be obtainedby assuming the impedance formulae toapply to a. varying instantaneous frequency.

This problem has been studied analyticallyby Carson and Fry, whose results may besummarised as follows. The response of alinear network may be represented by itsoverall transfer admittance, expressed asa complex function of steady-state angularfrequency by the- symbol Y ,( jw). If, now,the frequency becomes a function of time,the response may be denoted by Y(jw, t).This is, in general, different from the " quasi -stationary " admittance, YUS2), which isobtained by substituting the varying in-stantaneous frequency, Q, in the steady-state formulae. But it is shown that

Y(jw, 1) = Y(jS2) 8(t),*

where 8(t) is a correction series, containingthe time derivatives of the frequency, andthe derivatives of Y with respect to Q. IfQ = w + µ(t), and ic(t) = As(t), where A isthe frequency excursion and s(t) representsthe modulating signal, then, if the seriesconverges rapidly we have, taking onlythe first term,

2Y(jco, 1) = Y(IQ) +/2 d( jY.(2)2,

approximately.This is very nearly true if A is large comparedwith unity, if - i < s(t) s 1, and if thederivatives of s(t) are small. In manypractical cases, it is sufficient to assumethat Y(jw, t) = Y(j0). This assumption is

*" Variable Frequency Electric Circuit Theory."Bell System Technical Journal, October, 1937.


generally made in the design of discrimi-nators. If it is valid, the behaviour ofband-pass filters may be simply deduced.The admittance Y (j(2) may be representedas exp [a(S2) jil(S2)], and the input signalas expj f S2dt. The output signal is thereforegiven by

exp [a(Q) ji3(S2)] . exp gS2dt= exp x(S2) . exp j[ f Qdt p (Q)].

The amplitude factor, exp a(S2), may bedisregarded, since the limiter renders itconstant. To determine the effect of thephase factor, we observe that the instan-taneous frequency of the output wave isgiven by

3'

dt 13(D) = d-S2

w I,t(t)ddP

(t)

Now this is nearly true provided, as we havenoted, that the higher derivatives of µ(t)

are negligible and that di3is small. By

d S2Taylor's theorem we have

µ(t +T) =Ft(t) +Tµ'(t) +

253

the terms beyond the second on the rightbeing negligibly small. The modulationof the output frequency is, therefore, p.(t

dPprovided thatd-Q

is constant over the rangeof instantaneous frequencies present. Inother words, there is merely a time delaybut no distortion, if the phase characteristicof the network is linear. If it is not linear,considerable distortion may result.

Spectral analysis of a frequency modulatedsignal shows that, in general, an infinitenumber of sidebands is present. The limita-tions imposed above on A and s(t) imply thatmost of the energy of the wave lies in theband w + A.

To summarise, we may say that, if themaximum frequency excursion is manytimes the highest modulation frequency, areactive network will produce negligibledistortion if it has a linear phase character-istic, and an amplitude characteristic whichis nearly level over the range w ± A, where Ais the maximum frequency excursion. Theuse of " staggered " tuned circuits to producethe required amplitude characteristic isprecluded, since the phase shift is thennon-linear.

CorrespondenceLetters of technical interest are always welcome. In publishing such communications theEditors do not necessarily endorse any technical or general statements which they may contain

"The Temperature Compensation of Condensers."To the Editor, " Wireless Engineer "

SIR,-In the letters published in your May issuesome references were made to my article on " TheTemperature Compensation of Condensers " andin reply I would first like to thank Mr. Courseyfor his remarks on the value of the article and alsofor pointing out a further feature which precludesthe use of a ceramic element for the temperaturecompensation of a good quality condenser-thatof the poor frequency characteristic of permittivityof those ceramics which have highly negative tem-perature coefficients.

There are, of course, as Mr. Coursey mentions,alternatives to paraffin wax as an impregnant forpaper in the manufacture of condensers, a compre-hensive reference to which was, however, outsidethe scope of the article since this was devotedalmost entirely to the temperature compensationof condensers of high permanence.

My conception of the effect of excessive humidityupon a ceramic condenser was that of a very large

increase of permittivity in very thin surface layersat the boundaries of the electrodes. PresumablyMr. Coursey prefers to regard the effect as anindefinite extension of these electrode boundariesby surface moisture.

I am interested in Mr. Coursey's statement thatthe ceramic materials used in dielectrics show nowater penetration because, if this is so, his con-ception of the effect of humidity is probably themore correct. The result is the same, however,for whichever the cause the effect is an increaseof apparent permittivity of the material. Mr.Westcombe states that this humidity effect can bereadily overcome by enamelling the surface, butMr. Coursey says that immunity can be obtainedonly by complete hermetic sealing in an externalceramic casing and that this method is not readilyadaptable to " trimmer " condensers. The ceramiccompensator to which I referred in my article isnecessarily of the trimmer type and it would there-fore be difficult to apply hermetic sealing in this case,

Mr. Coursey, Mr. Tinckham and Mr. Westcombecriticised my statement that it is impossible to

ti

254WIRELESSENGINEER

adjust ceramic condensers accurately to nominalvalues. I agree with Mr. Tinckham that theaccuracy to which such condensers may be adjustedis comparable with that associated with the ordinarysilvered mica condenser and is indeed very goodfor the commercial purposes for which both typesare intended. However, the accuracy of ceramiccondensers of, say, i,000 p.p.F is variously adver-tised as io per cent. to 20 per cent. and accuraciesof the order 1 per cent. are stated as special.In one maker's catalogue 5 per cent. is stated to bea special accuracy. These figures compare veryunfavourably with the accuracies ordinarily ob-tained with high-grade mica condensers of thesame value. But perhaps I was a little unfair toform a comparison between mica standards andcommercial ceramics, the accuracy of which lattercould, no doubt, be improved were there any possi-bility of employing ceramic condensers as standards.

The commercial ceramic condenser has un-doubtedly filled a gap in condenser manufacturesince it is particularly suitable for low capacitancesof, say, less than 300-50o p4iF.

It is less satisfactory for higher capacitancesbecause, naturally, materials having higher permittivity must be employed --materials which havepermittivities highly variable with frequency.Such materials usually have temperature co-efficients of permittivity which are not only highbut also negative and therefore, for the reasongiven by Mr. Coursey, variable with frequency.Moreover, the power factors of such condensers(10-3) are five times those usually associated withmica standards (2 io-4) and may be as much asone hundred times greater than those of good airstandards (io-3). For these reasons the ceramiccondenser can hardly be regarded as a standardof capacitance.

General purpose standards of capacitance areusually required to have equally low power factorsat all frequencies and while this is possible with airand mica standards it certainly is not with ceramiccondensers-ceramics being essentially radio fre-quency dielectrics as stated in my article.

Other features of some ceramics which makethem unsuitable for use in standards of capacitancesuch as non -cyclic thermal behaviour, need notbe stressed as they are probably of less importancethan those already given.

In the penultimate paragraph of his communica-tion Mr. Westcombe criticises my statementthat . . . the capacitance of the ceramic con-denser has a tendency to dependence on humidity.''That there is at least a tendency is surely admittedin a statement by the makers of the ceramic com-pensator (which is a ceramic condenser) referredto on page 109 in my article, that In order toguard against the effects of atmospheric humidity,which tends to increase the capacity and also theloss factor, the regulators are protected by meansof an insulating lacquer. This affords certainprotection up to at least So per cent. relativehumidity." I am prepared to agree, however,that by recently developed methods the ordinarycommercial ceramic condenser of fixed capacitancetray kaeen rendered .fT)`iit)4 V immune from the effectof humidity.

Finally Mr. Westcombe states that 1 have

.1 till). 1)142

omitted Dr. Thomas's findings relating to the cttcctof assembly strains on temperature coetlic winOn the contrary 1 referred on page 1o( to DI-.Thomas s findings in his book Theo c aua 1), signot I 'a/ce Oscillators, pp. 154 - s2 section ofthe work deals exhaustively with the sut.jett inquestion.

Again, the curves B, C, 1), and F of I lg to-gether with line 10 of col. 1, p. m so and the finalparagraph of col. 1, p. 150 fully draw attention tothe existence of unexpectedly high rand thereforeunpredictable) temperature coefficients

The expressions which 1 gave forI

0-

were used for the evaluation of the telnIq'rat orecoefficients of very carefully constructed condemnersand were certainly only intended for use 0itli Fixedvalue laboratory air condensers of the highestgrade. W. H. F. GRIErl

Reigate, Surrey.

To the Editor,'' 11 licless Engine,'Sik,---Mr. Griffiths' article in the March issue Of

Wireless Engine, contains a number of idyl -elitesto ceramic condensers some of his statementsindicate incomplete contact with modern dr\ elop-ment.

It is stated that ceramic condensers are stillvery inferior to the best mica condensers, andthat temperature Coenalelas are of the order of-5- 150 parts million -C. 111 point of ta) I. a I all!,!t.

of materials is available of both negatir andpositive temperature coefficient of pccmittisity.For example, the titama-magnesia type of cccamric,with a permittivity of lo, a power factor ,tan 6, of0.0001 or less, and temperature cortfitient of per-mittivity of 5 40 to So parts million C, is a

substantially better dielectric than mica for manypurposes, particularly as the dielectric propertiesare maintained over a very wide temperaturerange.

High-grade radio frequency ceramics are entirelynon -porous, and there is no change in permittivitywith humidity. Surface films of moisture on ex-posed ceramic surfaces, or on thin varnish coatingsof ceramic condensers certainly, for obvious reasons.cause variation in effective capacitance. As lotmica and other condensers, the remedy is to protectthe dielectric by an adequate well -sealed outer case ;this is standard practice among condenser makerswhen high stability ceramic condensers are re-

quired. It may be mentioned also that ceramicsare now available which show great reduction inmoisture film formation under high humidity.

Mr. Griffiths states that accurate adjustment ofceramic condensers and inductance tolls withdeposited turns is impossible. This statement is,of course, inconsistent with experience in normalbulk production of both condensers and inductances.

The use of ceramic condensers for compensatingvariable air condensers may not be so satisfactoryfor high grade standards as the other methodsindicated. However, a high degree of compensationcan be achieved at all settings of the air condenserif an appropriate high -capacitance negative coal -Gent condenser is used in series, in addition to asmall parallel Connected compensation.

it


Incidentally, Mr. Griffiths' reference only toearly German ceramics would seem to indicate thathe is not acquainted with the range of Britishmaterials which have been available for severalyears. G. P. BRITTON

Steatite and Porcelain Products, Ltd.

Humidity Testing of Components.To the Editor, " Wireless Engineer "

SIR,-Mr. Westcombe has reopened the debatethat took place at the I.E.E. in November last, andI feel that his statements call .for some furthercomments and explanation.

In the first place I would emphasise that, inproperly designed test chambers, steam is not" blown on to " the radio components at all, butmerely serves to saturate the air in the test en-closure. In this connection I did not, perhaps,make it sufficiently clear in the article that the testapparatus arrangement depicted in Fig. 2 in thearticle does not represent one that is commonlyemployed in this country. The remarks that Imade concerning the greater reliability of the steaminjection method were referring primarily to testingapparatus of the type illustrated in Fig. 3 of thearticle. Unfortunately the angle from which thephotograph was taken caused the steam inlet pipeto be obscured. As Mr. Westcombe and othersmay not be familiar with the apparatus, it may beinstructive to amplify the description by the dia-grammatic sketch herewith, which shows the in-terior arrangement in section. The chamber sketched

REMOVABLE LID WITHTIGHT FITTINGOVERLAPPING JOINTS

STEAM INLETFROM BOILER

GAS SUPPLY

THERMOSTAT

TO GAS HEATERFOR BOILER

CONDENSATE RETURNTO BOILER

SHELF FORCOMPONENTS

STAND FORCOMPONENTS

Diagrammatic sketch of arrangement of pipeconnections to humidity test enclosure.

some i8in. cube, Made of sheet copper, tinnedinside, and polished outside. The lid is removablefor loading, and has an overlapping joint as sketched.The water vapour (or wet " steam ") is led inthrough the pipe A from the top of the " boiler "--or, as it should more correctly be termed, evapo-rator. This pipe passes through the side of thechamber close to the top and is turned straight down-wards almost to the bottom of the enclosure as at C.The water vapour or steam is thus not blown on tothe components under test, but impinges on to thebottom of the chamber, whence it _spreads fairly

25-5

uniformly over the entire area-as may quite easilybe seen by inspection of the " fog " inside whichresults if cold air is allowed to enter by lifting thelid for a few moments.

Articles are not placed on the bottom of the en-closure, but on the stand which is about Sin.above the floor, or on wire mesh shelves as sketched.Temperature control is obtained by the thermostat,the sensitive element of which, in the form of therod D, extends across the back of the enclosure,spaced some sin. from the side wall.

Tests with such enclosures show that there isnever more than 2 deg. C. difference in temperaturebetween any working part of the inside space-naturally excluding actual contact with the sidesor lid, and about Iin. away therefrom.

Water vapour condenses freely on the articlesunder test when they are put cold into the warmwet atmosphere, which is generally considered tobe the proper method of carrying out the test.Surplus condensate runs down the sides of theenclosure and drips off the articles, passing backto the boiler by the pipe B.

With apparatus of such construction, at leastwhen limited to the size mentioned, a very uniformtest atmosphere is obtained.

It is understood, however, that tendency inofficial quarters is towards circulation of the in-coming moisture stream by a fan. The criticismof Mr. Westcombe might apply more rightly tosuch arrangements than it does to the arrangementhere described and illustrated in Fig. 3 of myarticle.

Secondly, Mr. Westcombe thinks the use of suchapparatus cannot simulate even the most extremetropical conditions. An exactly opposite viewwas expressed during the discussion at the I.E.E.on this subject in November last. It was therestated that experience has shown that the Ki I°humidity test, carried out in this way, does veryclosely simulate average tropical use for about2 years (apart from any special local conditionssuch as salt air corrosion, etc.).

Thirdly, I do not quite see the point of Mr.Westcombe's simile of fatigue and tensile strengths.The Kilo type of test is a fatigue test in that itconsists of repeated cycles of temperature andhumidity. It most certainly does not have anycharacteristics of a static test (like his simile oftensile strength)-particularly when it is continuedfor longer periods, such as the twenty cyclesspecially mentioned on p. roo of my article.

Finally, it seems to me that while Mr. West-combe's test enclosure is better than many arrange-ments that have been used, it still suffers from thefundamental defect that if evaporation of the waterin the bottom of the chamber is to take place, itstemperature must be raised above that of the airabove its surface. Even with his water jacketarrangement, evaporation will still be required tocompensate for the condensation that must alwaystake place since the top of the enclosure is outsidethe water jacket, and some leakage may also occuraround the lid and certainly will take place if theenclosure is opened at all during use. In mosttesting laboratories dealing with any substantialnumber of components per day, opening of theenclosure during use can hardly be avoided. A

D.

256 WIRELESS June, 1942ENGINEER

large make-up of moisture in the air must thereforebe obtained by evaporation from the enclosedwater. Some auxiliary heating in the water thenbecomes almost imperative if the operating con-ditions inside the enclosure are to be maintainedwith any degree of uniformity. My experiencehas certainly been that this steam injection methodgives more reliable, consistent and repeatable resultsthan do evaporation methods from an internal watertrough, even although its effects are more severe.

Liss, Hants. PHILIP R. COURSEY.

Book ReviewsThermionic Valve Circuits

By EmRYS WILLIAMS, Ph.D., A.M.I.E.E. Pp. 174viii, with io6 Figs. Sir Isaac Pitman & Sons,

Ltd., Parker Street, Kingsway, London, W.C.2.Price 12s. 6d.

This book is based on a course of lectures tofinal year degree students in Electrical Engineering,and assumes the preliminary knowledge that suchstudents would possess, but for the benefit of thosewhose mathematics may be rusty, the first five pagesare devoted to a summary of the a.c. theory andmathematics required. Subsequent chapters dealwith the valve, amplifiers, regeneration and oscilla-tion, detectors and rectifiers, frequency changersand modulators. The book makes no claim tonovelty of treatment ; it is based on a selectionfrom larger and more comprehensive works, suchas Terman's Radio Engineering, of those parts deal-ing exclusively with thermionic valve circuits.

The book admirably fulfils its purpose. Theground covered and the method of treatment arevery suitable for this part of a University courseon radio -communication. It is, however, verysurprising and unfortunate in a book intended foruniversity students to find the a.c. resistance of avalve referred to throughout as its impedance.This usage is excusable among those who cannot beexpected to have much knowledge of a.c. theorybut is hardly excusable in a book of this type. Theslope of the static characteristic gives a value ofSVa/SIa which is sometimes called the differentialresistance and sometimes the slope resistance, butto which the British Standards Institution officiallygave the name of a.c. resistance. It is obtainedfrom a static characteristic determined with steadyvoltages and currents ; it has nothing to do withinductance or capacitance ; it is entirely independ-ent of frequency, and it is universally representedby R or p and never by Z. One can easily under-stand how the non -mathematical person would bemisled into thinking that the mysterious symbol8V/SI could not represent a resistance. To beconsistent the author should have called ga, themutual admittance. The author May plead inextenuation that many of the valve manufacturersuse the term, which is true, but a poor argument.Apart from this the book is one that can be thor-oughly recommended to the large number of stud-ents who are now having, willy-nilly, to study thethermionic valve and its many applications in allour universities and technical colleges.

G. W. 0. H.

The Cathode Ray Tube and its ApplicationsBy G. PARR. Pp. 18o with 8o Figs. Chapman &

Hall, Ltd., 11, Henrietta Street, London, W.C.2.Price 13s. 6d.

One wonders if the author has any conception ofthe impression made on the average reader when, onthe first page of a book making some claim toscientific accuracy, he finds the early work on nega-tively charged particles attributed to somebodynamed J. J. Thompson, due presumably to someconfusion between J. J. and Silvanus. The additionof " Kelvin " in brackets would have completedthe triangle. Perhaps, however, one should not betoo critical, as the author explains in the prefacethat, due to circumstances beyond his control, therevision of the earlier edition had to be suddenlyaccelerated. The first edition was entitled " Thelow voltage cathode ray tube," but in this newedition the limitation has been removed. Thescope of the book will be seen from the titles of theeight chapters : I. Construction and Operation ;II. Focusing and Performance ; III. Lissajous'Figures ; IV. Linear Time Bases ; V. Other TimeBases ; VI. Applications to Radio Engineering ;VII. Industrial and Other Applications ; VIII.Television Reproduction. There is an appendixdealing with Photography. As in the earlier edition,one of the most valuable features is the very com-plete and extensive bibliography occupying 17

pages. Another valuable feature is the list ofcomponents for building up the various circuitsdescribed ; this will prove very helpful in labora-tory work. In many places we felt that the authormight with advantage have given a little moreexplanation. On p. 7, for example, we are told thatin the Standard Telephone Co.'s soft tubes, thegrid is made positive with respect to the cathode." This electrode then acts as a ' pre -concentrator,'the positive potential being necessitated by thegeometrical position of the cylinder and cathode."There is no explanation as to why it is called a pre -concentrator or how it pre -concentrates. Again,on p. 17 it is stated that " to prevent fluctuationsin the beam current from affecting the bias voltagea ' bleeder ' resistance should be connected acrossthe H.T. supply terminals as shown (Fig. 8 (b))."The only current through the tapped bias resistanceis the beam current, and it is not at all clear howthis is modified by the presence of the so-called" bleeder resistance " across the H.T. terminals.Fig 8 (a) appears to be upside down when comparedwith (b) and (c). On p. 26 with reference to therotation of the image of the electron source by thefield it is stated that " the focusing coil of Fig. 13 (c)is designed to obviate this effect " ; but no hint isgiven as to how it does it. Limitations of space areprobably to blame for these shortcomings. In copy-ing Fig. 68 from Cosens' original diagram an essen-tial connection has been omitted.

The book contains a great amount of very usefulinformation, and will prove very helpful at thepresent time when so many cathode-ray tubes arebeing used in radio and other laboratories. The listsof necessary components will enable one to go to thecupboard and get out the various items, and connectthem up in the shortest possible time, while theclassified bibliography will enable one to look up theliterature on any specific point. G. W. 0. H.

WIRELESSENGINEER

D/F Handbook for Wireless Operators11 By W. E. CROOK. Pp. v 64 with 85 Figs.Sir Isaac Pitman & Sons, Ltd., Parker Street,Kingsway, Lcindon, W.C.2. Price 3s. 6d.

This is a strictly practical book intended forwireless operators employed at D/F stations. Itassumes a knowledge of elementary radio theory.Specific D/F apparatus is not referred to, because,as the author says, nothing would be gained bydescribing one or two actual sets which will inevit-ably be obsolete in a comparatively short time.After an introductory chapter on D/F in general,Chapter II deals with the rotating frame, Chapter IIIwith the Bellini-Tosi system, Chapter IV withfixing the sense as well as the direction of thesignal, and Chapter V with the various errors andtheir elimination by the use of Adcock aerials.The final chapter explains the choice of a suitablesite for a D/F station and its calibration by meansof a local oscillator or by means of aircraft. Tojudge from the fact that it is not mentioned, we

presume that the Robinson D/F coil is a thing of the4past.

The book is very well produced, well illustrated,..;and, we believe, entirely free from misprints. The, description of the apparatus and the explanation

f the various phenomena and their effects areodels of clarity. The only thing that we would

criticise is the drawing that is here reproducedas (a). It is Fig. 6 in the book. This can mean either,of two diametrically opposite things depending onwhether you picture it as an inside or outside viewf a corner of a cube. The two alternatives are

illustrated in (b) and (c). If one adopts the hand -rule, pointing the first finger along the magneticeld and the second finger along the electric field,

then for the thumb to indicate the direction oftransmission, (b) corresponds to the lefthand and

257

(c) to the right hand. Which is correct can be seenat once from the simple circuit shown in (d). Here

IS IT LIKE OR LIKETHIS? THIS?

( b )

++ H ++

at oncewhich is

( d")

E

(c)

the electric field isupward and theenergy transmis-sion from right toleft as in the otherfigures and the mag-netic field is seen

to be away from the observer as in (b)therefore the correct picture.

G. W. 0. H.

T.

I.E.E. Wireless Section CommitteeTHE following nominations have been made

to fill the vacancies which will occur on theWireless Section Committee of the Institu-

tion of Electrical Engineers on September 3oth :-Chairman, R. L. Smith -Rose, D.Sc., Ph.D. (NationalPhysical Laboratory) ; Vice -Chairman, H. L.Kirke (British Broadcasting Corporation) ;Ordinary Members of Committee, A. D. Blumlein,B.Sc.(Eng.), (Electric and Musical Industries) ;E. C. S. Megaw, B.Sc. (General Electric Co.),and J.'A. Smale, B.Sc. (Cable & Wireless).

Wireless PatentsA Summary of Recently Accepted Specifications

The following abstracts are prepared, with the permission of the Controller of H.M. Stationery Office, from3pecifications obtainable at the Patent Office, 25, Southampton Buildings, London, W.C.2, price If- each

,kCOUSTICS AND AUDIO -FREQUENCY CIRCUITSAND APPARATUS

1542 408.-Automatic biasing arrangement, say forpt5 power amplifier, combined with an additional~ ource of bias as a safeguard against failure of theirst.

I J. W. Dalgleish and S. R. Poole. Application date7th February, 1940.

AERIALS AND AERIAL SYSTEMS4142 241.-Frame aerial, particularly for portableets, in which a series inductance is utilised toeduce the effect of distributed capacitances both

between the turns of the aerial, and from aerial toground.

Philco Radio and Television Corpn. (assignees ofW. H. Grimditch). Convention date (U.S.A.)17th June, 1939.

542 452.-Transmission-line filter, including piezo-electric crystals each capable of resonating at oneor other of several frequencies.

Standard Telephones and Cables (assignees ofW. P. Mason). Convention ,date (U.S.A.) lothNovember, 1939.

542 780.-Transmission-line coupling circuit for


converting push-pull energy into a push -pushrelation.

111arconi's W.T. Co. (assignees of N.E. Lindenblad).Convention date (U.S.A.) 28th July, 1939.

DIRECTIONAL WIRELESS

542 564. -Direction -finding systemmagnetic disc rotates with a framepoles so induced control the positionindicating magnet.

Standard Telephones and CablesN. E. Klein). Convention - dateOctober, 1939.

in which aaerial and theof a direction -

(assignees of(U.S.A.) 25th

542 584. -Indicator- device for a direction finder inwhich transparent and opaque scales are providedto simplify the taking of a bearing corrected for" sense " and for quadrantal error.

Marconi's W.T. Co. and J. H. Moon. Applicationdate 17th July, 1940.

RECEIVING CIRCUITS AND APPARATUS(See also under Television)

542 223. -Inductance and capacitance unit fortrimming the tuning of ganged high -frequencystages.

Marconi's W.T. Co. ; C. P. Beanland ; andC. S. Cockerell. Application date 28th May, 1940.542 356. -Time -constant circuit inserted in serieswith the high-tension supply to an amplifier torender it immune from voltage fluctuations.

W. W. Groves (communicated by Automatic SignalCorpn.). Application date 4th March, 1940.542 395. -Variable inductance which is tuned byuniformly changing the spacing of the coils byaltering the pressure of a spring at one end.

The Mullard Radio Valve Co. and C. C. Eaglesfield.Application date- 14th August, 1940.542 469. -Single -valve arrangement including atuned circuit of variable band -width as determinedby the application of positive feed -back to thecircuit and negative feed -back to the valve.

E. L. C. White and E. W. Bull. Application date8th June, 1940.542 485. -Coupling circuit designed to eliminate theeffect of intermediate -frequency instability in amulti -band superhet receiver.

Marconi's W.T. Co. ; C. S. Cockerell ; J. D.Brailsford ; and M. H. Cufflin. Application date23rd February, 1940.542 531. -Powdered -core inductance unit whichcan be tuned over a wide range without anyappreciable change in the inductance -resistanceratio or " Q " factor.

Marconi's W.T. Co. (assignees of A. L. Rosenberg,Junr.). Convention date (U.S.A.) loth July, 1939.542 611. -Securing a constant " band -spread "effect over a wide frequency range by varying anauxiliary inductance which does not form part ofthe main tuning circuit but is coupled to it.

The Mullard Radio Valve Co. ; F. Caplin ; andC. E. Payne. Application dates 9th July, 1940,and 18th February, 1941.

June, 1942

542 675. -Phase -shifting network associated withthe grid circuit of a valve and particularly suitablefor automatic frequency -control or for frequencymodulation.

The General Electric Co. and L. C. Stenning.Application date 2nd August, 1940.

TELEVISION CIRCUITS AND APPARATUSFOR TRANSMISSION AND RECEPTION

542175. -Broad band repeater section, includingstabilised negative feed -back for the transmissionof television signals or multi -channel carrier systems. c

Standard Telephones and Cables (assignees ofH. W. Bode). Convention date (U.S.A.) 29thSeptember, 1939.542 2I9. -Construction and arrangement of theelectrostatic deflecting -plates for preventing dis-tortion in a television transmitting tube using alow -velocity scanning beam.

Marconi's W.T. Co. (assignees of H. A. Iams and iA. Rose). Convention date (U.S.A.) 27th May, 1939.542 258. -System of interlaced scanning for tele-vision which readily lends itself to a completeseparation of the vertical and horizontal syn-chronising impulses.

Standard Telephones and Cables (assignees ofR. L. Campbell). Convention date (U.S.A.) 19thOctober, 1939.

242 259. -Television receiver with interlaced scan-ning in which vertical synchronising impulses areseparated from horizontal synchronising impulses,without the latter having to be intermittentlyblanked out.

Standard Telephones and Cables (assignees of ;.

R. L. Campbell). Convention date (U.S.A.) 22nd ilDecember, 1939.

542 332, -Television transmitter tube using a low -velocity scanning beam and provided with meanswhereby only those electrons that have beenmodulated are utilised for signalling.

Marconi's W.T. Co. (assignees of .H. A. lams).Convention date (U.SA) 29th July, 1939.542 436. - Distribution system for graduallychanging -over or " fading " one television scene,'.into another.

Pliilco Radio and Television Corpn. (assignees ofB. .E. Schnitzer). Convention date (U.S.A.) 'iithMay, 1939.542 626. -Means for securing an automatic ampliification control and a stable line -synchronisingimpulse in television.

Hazeltine Corpn. (assignees of R. L. Freeman andH. L. Blaisdell). Convention date (U.S.A.) 8thDecember, 1939.

TRANSMITTING CIRCUITS AND APPARATUS(See also under Television)

i

541 634. -Transmission network comprising three'sections in series -shunt for coupling loads of differentimpedances.

Electrical Research Products, Inc. Conventiondate (U.S.A.) 4th August, 1939.

June, 1942(

541 664. -Electrode arrangement of a dischargetube for generating ultra -short waves by projecting

) a stream of electrons through a resonating chamber.Standard Telephones and Cables and F. D.

Goodchild. Application date 4th June, 194o.

541 665. -Transmission system in which a commoncarrier wave is utilised to carry different messages,one by a form of amplitude modulation and theother by a method of phase or frequency modulation.

Standard -Telephones and Cables ; W. A. Beatty ;and C. T. Scully. Application date 4th June, 1940.

541 796. -Short-wave radio relay systems in whichthe signal is received and retransmitted withoutchange of frequency.

Marconi's W.T. Co. (assignees of H. 0. Peterson).Convention date (U.S.A.) 30th June, 1939.

541.882. -Means for correcting amplitude andphase distortion in transmission systems covering a

(wide band of frequencies [addition to 495 8,5].Electric and Musical Industries. and J. Collard.

,Application date 13th June, 1940.

542 005. -Transmitting and receivinat' signals by amethod in which the polarisation of the waves inspace is made to oscillate about a mean position.

Marconi's W.T. Co. (assignees of G. L. Usselman).Convention date (U.S.A.) 17th June, 1939.

542 226.-" Passive " network for coupling amodulating device to an oscillation -generatorwithout generating parasitic frequencies.

Standard Telephones and Cables (communicated byLe Materiel Telephonique Soc. Anon.). Applicationdate 30th July, 1940.

i542 277. -Grid -modulated oscillator circuit, par-ticularly for low -powered battery -operated trans-mitters.

J. W. Dalgleish ; S. R. Poole ; and Pye.Application date 7th February, 194o.

i

CONSTRUCTION OF ELECTRONIC -DISCHARGEliDEVICES542 182. -Ultra -short-wave arrangement of reso-nators for first " bunching " a stream of electronsand then drawing power from it.

Marconi's W.T. Co. (assignees of I. Wolff).Convention date (U.S.A.) 21st July, 1939.

5, 285. -Construction and arrangement of the;split anodes in a high-powered magnetron.) Marconi's W.T. Co. (assignees of G. R. Kilgore).Convention date (U.S.A.) 30th June, 1939.

't. 542 389. -Electron -discharge device of the Klystron:type in which a beam of positive ions is utilised toLkincrease the density of a stream of electrons.

Standard Telephones and Cables and H. Motz.Application date 5th July, 1940.

542 390. -Means for neutralising the space chargesset up by the electron stream in a resonator tubeof the Klystron type.

Standard Telephones and Cables and H. Motz.Application date 5th July, 1940.

WIRELESSENGINEER

259

542 488. -Means for controlling the intensity of anelectron stream by first diverting it from its pathand then restoring it to a path parallel with the first.

J. D. McGee ; H. Miller ; and G. S. P. Freeman.Application date 2nd May, 1940.542 496. -Means for removing from 'a spiral streamof electrons those travelling in a path of undesirablylarge radius.

J. D. McGee and G. S. P. Freeman. Applicationdate 2nd May, 1940.542 497. -Means for centring the electron streamin a cathode-ray tube utilising both electrostaticand electromagnetic deflecting fields.

J. D. McGee and G. S. P. Freeman. Applicationdate 2nd May, 1940.542 908. -Construction and arrangement of theresonant electrodes of a tube in which an electronstream is first bunched and then utilised as asource of high -frequency energy.

Standard Telephones and Cables (assignees of C. V. Litton). Convention date (U.S.A.) 14th

December, 1939.

542 970. -Arrangement for " bunching " the elec-tron stream in an oscillation -generator and forfeeding the output to a " horn " aerial or radiator.

Marconi's W.T. Co. (assignees of W. van B.Roberts). Convention date (U.S.A.) 28th July, 1939.

SUBSIDIARY APPARATUS AND MATERIALS

542 245. -Magnifying arrange.ment for viewingoptical images produced by the electron bombard-ment of a fluorescent screen.

Electric and Musical Industries ; J. D. McGee ;and H. G. Lubszynski. Application date 27th June,1940.

542 352. -Selector switch for automatically settinga wireless receiver to receive a desired programmeat any given time over a sequence of days.

A. B. Thomsen. Convention date (Denmark)16th May, 1938.542 366.-Thermionic valve circuit adapted to givea constant output of trapezoidal form irrespectiveof variations in the applied input.

B. M. Hadfield. Application date 6th July, 1940.542 806. -Construction and arrangement of arotary indicator, or tab -holder, particularly suitableas a tuning dial in a wireless receiver.

Philco Radio and Television Corpn. (assignees ofJ. H. Pressley). Convention date (U.S.A.) 25th July,1939.

543 000. -Earthing switch for minimising theradiation of " static " disturbance when starting -upan internal-combustion engine.

Bendix Aviation Corpn. Convention date (U.S.A.)2nd August, 1939.543 op. -Trembler or vibrator system for trans-forming the voltage derived from a direct -currentsource, particularly for the high-tension supply towireless sets.

Philco Radio and Television Corpn. (assignees ofJ. H. Pressley). Convention date (U.S.A.) 8thSeptember, 1939.

26o WIRELESS June, 1942ENGINEER

Abstracts and ReferencesCompiled by the Radio Research Board and reproduced by arrangement with the Department

of Scientific and Industrial Research

For the information of new readers it is pOinted out that the length of an abstract is generallyno indication of the importance of the work concerned. An important paper in English, in ajournal likely to be readily accessible, may be dealt with by a square -bracketed addition to thetitle, while a paper of similar importance in German or Russian may be given a long abstract.In addition to these factors of difficulty of language and accessibility, the nature of the work has,of course, a great influence on the useful length of its abstract.

PAGE PAGE

Propagation of Waves ... 260 Directional Wireless 271

Atmospherics and Atmospheric Acoustics and Audio -Frequencies... 272Electricity 262 Phototelegraphy and Television ... 274

Properties of Circuits 263 Measurements and Standards ... 276Transmission 265 Subsidiary Apparatus and Materials 279Reception ... 266 Stations, Design and Operation ... 283Aerials and Aerial Systems 268 General Physical Articles ... 284Valves and Thermionies 268 Miscellaneous 284

PROPAGATION OF WAVES

1592. ELECTROMAGNETIC WAVES IN METAL TUBESOF RECTANGULAR CROSS-SECTION.-J. Kemp.(Elec. Communication, No. 2, Vol. 20, 1941,pp. 73-79.) See 2958 of 1941.

1593. ON THE RELATION BETWEEN THE INHERENTVALUES OF HOLLOW METAL TUBES ANDTHEIR MISCELLANEOUS CONSTANTS [Exten-

1594.

1595.

sion of Work on Rectangular - SectionTubes (1817 of 1941) to Fan -Shaped Tubes,as Example of Cylindrical -Coordinate Sys-tem].-I. Iwataka. (Electrotech. Journ.[Tokyo], March 1941, Vol. 5, No. 3, pp. 58-59.)

ELLIPTIC AND SPHEROIDAL WAVE FUNC.TIONS [Scalar & Vector Wave Equations :Gegenbauer Functions : General SpheroidalFunctions : Prolate & Oblate SpheroidalFunctions : Mathieu Functions].-L. J. Chu& J. A. Stratton. U OUM. of Math. 6 Phys.[of M.I.T.], Aug. 1941, Vol. 20, No. 3,pp 259-3994GENERAL AMPLITUDE RELATIONS FOR TRANS-MISSION LINES WITH UNRESTRICTED LINEPARAMETERS, TERMINAL IMPEDANCES, ANDDRIVING POINT.-King. (See 1743.)

1596. THE CALCULATION OF GROUND -WAVE FIELDINTENSITY OVER A FINITELY CONDUCTINGSPHERICAL EARTH [Summarised Results'of 1936/39 Papers, and Graphical Methods(with Curves & Transparent Log -LogGraph Sheets) for Practical Computation,for Vertical & Horizontal Polarisations :Examples of 5oo kc/s over Sea Water,I Ito kc/s over Land, & 46 Mc/s over Land :Appendices on Height -Gain Function, etc.].

-K. A. Norton. (Proc. I.R.E., Dec. 1941,Vol. 29, No. 12, pp. 623-639.)

" It has been found experimentally (1597, below)that the departures from these idealised conditions,such as hills, buildings, trees, etc., cause largevariations from the calculated values at particulardistances, but the theory does provide an excellentguide to the average fields encountered in practice."1597. FIELD -INTENSITY SURVEY OF ULTRA -HIGH -

FREQUENCY BROADCASTING STATIONS [Re-port to F.C.C.].-E. W. Chapin & K. A.Norton. (Referred to in 1596, above.)

1598. CORRECTION TO THE EFFECT OF THEEARTH'S CURVATURE ON GROUND -WAVEPROPAGATION " [Correction to Expressionfor Distance Parameter for HorizontallyPolarised Waves].-C. R. Burrows & M. C.Gray. (Proc. I.R.E., Feb. 1942, Vol. 3o,No. 2, p. 105.) See 1834 of 1941.

1599. ON THE DIELECTRIC CONSTANTS OF IONISEDGASES AT MEDIUM RADIO - FREQUENCY[Wavelengths 265-827 m : Air & Helium].-S. R. Khastgir & C. Choudhury. (IndianJourn. of Phys., Feb. 1941, 'Vol. 15, Part 1,pp. 63-71.)

For previous work see 92 of 1941. Szekely (1930Abstracts, p. 3o) used a resonance method with thetest condenser inside the discharge tube : con-ductivity and positive -ion -sheath effects wouldbring in complications liable to influence the results-which included the obtaining of dielectric con-stants of ionised air always greater than unity. Thewriters employ a condenser with its plates touchingthe outer tube surface, and a d.c. discharge froman induction coil. The double -beat procedure wasused, with a vernier air condenser made out of aspherometer.

Keeping the wavelength constant at about

iS

J une, 1942 WIRELESSENGINEER

700 m and varying the discharge current from0.25 mA to 1.8 mA (air) and 1.4 mA (helium), ewas found to increase from 1.015 to 1.082 (air) andfrom r.0062 to 1.038 (helium), the increase beingalmost linear in both cases for the greater partof the current range but slowing down (for air)beyond about 1.25 MA : a similar lessening ofthe increase in helium may perhaps be detectedat the end of the current range (Fig. 2, top curve)and it is deduced that both for air and helium e" increased linearly with the discharge currentexcept when the latter was large."

Keeping the discharge current constant and in-creasing the wavelength, it was found that E forboth gases decreased slowly and gradually as thewavelength increased, always however remainingslightly greater than unity : whereas test experi-ments showed that for wavelengths smaller thanabout 9 m for ionised air (keeping the dischargecurrent at a small steady value) was definitely lessthan unity. " This suggests the existence of aresonance frequency for the ionised medium muchhigher than the medium radio -frequencies employedin these experiments " : Gutton's quasic-elasticresonance and Tonks and Langmuir's plasma -electronic resonance would both be possible inthe medium inside a discharge tube, the differencebeing that in the first case (002 = A.N1, and in thesecond case 0,02 = B.N, where too is the resonancefrequency higher than the test frequency w. " Henceit can be seen from the expression for the dielectricconstant that if w is fixed, and N is increased byincreasing the discharge current, e would increaseproportionately except for the higher currents,"when N would be greater and consequently w,,would be higher, so that e would assume smallervalues than those demanded by a linear relationbetween e and N. " This is exactly what wasobserved."

1600. ON THE HIGH -FREQUENCY CONDUCTIVITYAND EFFECTIVE DIELECTRIC CONSTANT OFELECTRONIC MEDIUM IN A HIGH -VACUUMTHERMIONIC VALVE.-Basak. (See 1688.)

1601. ON THE MOTION OF AN ELECTRIC PARTICLE.-I. Opatowski. (fourn. of Math. & Phys.[of M.I.T.], Dec. 1941, Vol. 20, No. 4,pp. 418-424.)

After referring to the work of Stormer and Graef& Kusaka, the writer says : " In the present paperthe particle is assumed to move in electric andmagnetic fields of a very general form which includethe most important fields of mathematical physics(fields symmetric about an axis, plane fields, etc.) ;forbidden regions are determined and cases areindicated where the equation of motion can besimplified or explicitly integrated " : an exampledeals with a field due to a magnetic dipole and aring of electricity, and obtains " a forbidden regionfor the motion of an electric particle due to asimultaneous action of a magnetic dipole, a circularelectric current of constant intensity, and anelectrostatic charge distributed uniformly over acircle " [of interest in connection with cosmic rays].Boggio's work (394o of 1938 and 113o of 1939) isspecially referred to.

261

1602. A PHOTOGRAPHIC METHOD OF ESTIMATINGTHE MASS OF THE MESOTRON [and Experi-mental Support to Carlson & Schein'sAssumption that Totality of Cosmic RayProcesses in Atmosphere can be explainedas due to Impact of Single Primary Particle].-D. M. Bose & B. Choudhuri. (Nature,14th March 1942, Vol. 149, p. 302.) See2356 of 1941.

1603. NEW RESULTS CONCERNING THE APPEARANCEOF ATOMIC LINES IN THE AURORA BOREALIS.-L. Vegard & E. Tonsberg. (GerlandsBeitritge zur Geophysik, No. 3/4, Vol. 57,1941, pp. 289-309.)

1604. MAXIMUM VALUES OF THE EARTH -CURRENTVOLTAGES IN. THE NEIGHBOURHOOD OF THENORTH AURORAL ZONE DURING VERY IN-TENSIVE GEOMAGNETIC DISTURBANCES [ofMarch 1940: exceeding 5o -6o Volts/Kilo-metre : Comparison with Disturbance ofApril 1938].-L. Harang. (Gerlands Beitragezur Geophysik, No. 3/4, Vol. 57, 1941,pp. 310-316.) Cf. McNish, 15 of 1941.

1605. IONOSPHERIC -INVESTIGATIONS AT HUANCAYO1VIAGNELIC OBSERVATORY (PERU) WITH APPLI-CATION TO WAVE -TRANSMISSION CONDITIONS[using Carnegie Institution's AutomaticMulti -Frequency Equipment : Analysis ofResults in terms of Max. Usable Frequenciesfor Various Distances].-H. W. Wells.(Proc. I.R.E., Dec. 1941, Vol. 29, No. 12,p. 667: summary only.)

1606. TEMPERATURE OF METEORS AND DENSITY OFTHE UPPER ATMOSPHERE.-J. Hoppe. (Sci.Abstracts, Sec. A, Dec. 1941, Vol. 44, No. 528,PP. 375-376.)

1607. WHISTLING METEORS : A DOPPLER EFFECTPRODUCED BY METEORS ENTERING THEIONOSPHERE [Investigation prompted byObservation of Weak Heterodyne Whistlesof Unusual Type (High -Pitched Note rapidlyDescending in Pitch) in Short -Wave Recep-tion].-Chaman Lal & K. Venkataraman.(Electrotechnics [Bangalore], Nov. 1941, No.14, pp. 28-39: summary in Nature, I1thApril 1942, Vol. 149, pp. 416-417.)

1608. A POSSIBLE INTERPRETATION OF CERTAININTENSE RADIATIONS FROM THE NIGHT SKYIN THE ULTRA -VIOLET REGION [may belongto the Herzberg Bands].-J. Dufay. (ComptesRendus [Paris], 25th Aug. 1941, Vol. 213,No. 8, pp. 284-286.)THE POSSIBLE PRESENCE OF BANDS OF THELYMAN SYSTEM OF THE NITROGEN MOLECULEIN THE ULTRA -VIOLET RADIATION OF THENIGHT SKY.-G. Dejardin. (Comptes Rendus[Paris], 8th Sept. 1941, Vol. 213, No. Io,pp. 36o-363.)

1610. DAILY SOLAR RADIANT ENERGY AT THEEXTERIOR OF THE ATMOSPHERE.-R. E.Kennedy. (Sci. Abstracts, Sec. A, Dec. 1941,Vol. 44, No. 528, p. 376.)

1609.


1611. THE MOTION OF GASES IN THE SUN'S ATMO-SPHERE : PART II-ON THE WESTWARDTILT OF PROMINENCES [Usual, though East-ward Tilt & No Tilt can occur : Rejection ofPrevious Explanations : Explanation basedon Initially Radial Projection from DeepInterior].-A. K. Das & B. G. Narayan.(Indian Journ. of Phys., Feb. 1941, Vol. 15,Part 1, pp. 15-26.) Cf. d'Azambuja, 1290of May.

1612. ON THE SLOPE OF THE TROPOPAUSE AND ITSVARIATIONS.-L. Cagniard. (Comptes Rendus[Paris], 7th July 1941, Vol. 213, No. 1,pp. 34-37.) Further development of 638 ofMarch.

1613. ON THE THEORY OF CYLINDRICAL ANDSPHERICAL WAVES IN FRICTIONLESS GASESAND LIQUIDS.-H. Marx. (Ann. der Phys.,Feb. 1942, Vol. 41, No. r, pp. 61-88.) Onthe physical implications of some of Bechert'sresults (2361 of 1941 and 20 of January).

1614. THE CINEMA INTEGRAPH IN INTERREFLECTIONPROBLEMS.-Hedeman. (See 1831.)

ATMOSPHERICS AND ATMOSPHERICELECTRICITY

1615. AIRCRAFT PRECIPITATION -STATIC RADIO IN-TERFERENCE .-Starr. (Journ. Roy. A ercrn.Sot., April 1942, Vol. 46, No. 376, pp. 127-128 : summary only.)

1616. THEORY OF THE FORMATION OF A LIGHTNINGSTROKE.-S. Szpor. (Bull. de l'Assoc. suissedes Elec., 14th Jan. 1942, Vol. 33, No. 1,pp. 6-15: in French.)

Schonland's hypothesis has been developedquantitatively by Meek & Loeb, " but satisfactoryproofs have not been given. On the contrary,various phenomena observed in the laboratoryhave thrown doubt on the mechanism of the in-visible ionising discharge. In the first place it isdifficult to explain why the photoelectric ionisationahead of the front should not assure, without anypreliminary ionisation, a rapid development of thechannel. On the other hand, the effect of recom-bination should not be envisaged separately, apartfrom the contrary influence of thermal ionisation.With a current of about o.i A and a gradient upto 3o 000 v/cm or even more, according to thetheory, the channel is heated by a considerablepower, and a strong deionisation is not at all pro-bable.

" It will be shown that the arrests of the strokescan be caused by the diminution of the gradientahead of the channel front, thanks to the falls ofpotential along the channel. Since satisfactorydata for calculating this gradient are lacking, itwill be necessary to direct our studies in thisdirection. At the same time we shall obtainrelations between several quantities : the chargein the preliminary channel, intensity of the primaryelectric field and length of channel, current of thepreliminary discharge, and velocity of propagationof the front. It is evident that these relations cancontribute to a more far-reaching explanation ofthe lightning mechanism.

June, 1942

" Before this study we shall briefly set out themodern theory of the development of the dischargechannel, so that the picture may be more complete.The problem of the diameter of the channel re-quires to be considered with 'a special attention,in view of the present lack of a satisfactory explana-tion. In addition, the special conditions of theatmospheric discharges are defined by the primaryfield and by the influence of rain -drops." Nearlyforty literature references are given.

1617. SYMPOSIUM ON LIGHTNING ARRESTERS.-A. Roth, K. Berger, & others. (Bull. Assoc.suisse des Elec., 19th Dec. 1941, Vol. 32,No. 25, pp. 689-711.)

1618. ON THE POINT DISCHARGE IN THUNDER-STORMS AND SHOWERS [Measuring Equip-ment, Results, & Deductions : High SpaceCharges found near Ground are caused byPoint Discharges : Potential Drops atSurface yield No Reliable Conclusions asto Distribution in Cloud except in con-junction with Such Measurements : etc.].-C. W. Lutz. (Gerlands Beitrage zur Geo-physik, No. 3/4, Vol. 57, 1941, pp. 317-333.)

1619. THE POTENTIAL DROPS DURING THUNDER-STORMS [Comparison of South African &Indian Results with Those at Wahnsdorf& Potsdam, which showed both " Wilson "& " Simpson " Types about equally, butonly as Small Percentage of Total Number :Bipole Picture Not Generally Valid : etc.].

M. Krestan. (Gerlands Beitrage zurGeophysik, No. 3/4, Vol. 57, 1941, pp. 334-356.)

1620. THE YEARLY VARIATION IN THE DAILYCOURSE OF THE ATMOSPHERIC -ELECTRICALPOTENTIAL DROP IN WAHNSDORF ANDPOTSDAM. - H. Goldsehmidt. (GerlandsBeitrage zur Geophysik, No. 3/4, Vol. 57,1941, PP. 384-395.)

1621. ON THE NEED FOR, AND THE POSSIBILITY OF,AN ATMOSPHERIC - ELECTRICAL AEROLOGY'[Utility of Multi -Seater Glider : Use ofParachute -Borne Apparatus : the Mecklen-burg " Type 1939 ". (weighing only 4.4 kg)with Film -Recording String Galvanometer :etc.].-P. Lautner. (Gerlands Beitrage zurGeophysik, No. 3/4, Vol. 57, 1941, pp. 357-364.) With 18 literature references : seealso 1622, below.

1622. THE MEASUREMENT OF THE POTENTIALGRADIENT AND THE SPACE CHARGE IN THEFREE ATMOSPHERE [and a " ParticularlySmall & Stable Recording Electrometer 'for Throwing from an Aeroplane].-W.Mecklenburg & P. Lautner. (Sci. Abstracts,Sec. A, Dec. 1941, Vol. 44, No. 528, p. 379.)See also 1621, above.

1623. THE APPLICATION OF NEW RESULTS CON-CERNING INTERCHANGE PROCESSES [Atmos-pheric Turbulence Research : to Two Atmos-pheric -Electrical Problems, the Distributionof Radioactive Matter in the Atmosphereand the Layer Thickness of the " Electrode

June, 1942

1624.

WIRELESSENGINEER

Effect " for Linear Interchange -Variationwith Height].-H. Lettau. (Gerlands Beit-rage zur Geophysik, No. 3/4, Vol. 57, 1941,pp 365-383.)CONDENSATION NUCLEI AND SMALL IONS INTHE AIR OF COL D 'OLEN (2900 m ABOVESEA LEVEL) : also INVESTIGATIONS ON HEAVYIONS IN THE ATMOSPHERE : III [includingConnection with Relative Humidity &Visibility], and IONS AND NUCLEI, A CRITICALSTUDY.-G. Aliverti : H. Israel : H. Israel.(Gerlands Beitrage zur Geophysik, No. 3/4,No. 57, 1941, pp. 239-282.)

1625. ON THE CALCULATION OF THE IONISATIONEQUILIBRIUM IN NUCLEUS -CARRYING AIR.-E. von Schweidler. (Gerlands Beitragezur Geophysik, No. 3/4, Vol. 57, 1941, pp.283-288.)

1626. " WEATHER ANALYSIS AND FORECASTING :A TEXTBOOK ON SYNOPTIC METEOROLOGY "[Book Review].-S. Petterssen. (Nature,21st March 1942, Vol. -149, pp. 313-314.)

PROPERTIES OF CIRCUITS1627. ON THE COUPLED OSCILLATIONS OF A HAR-

MONIC OSCILLATING CIRCUIT AND A GENERA-TOR OF DISCONTINUOUS OSCILLATIONS [e.g.Dynatron], and THE FLUCTUATIONS INAUTO -OSCILLATING SYSTEMS AND THE DE-TERMINATION OF THE FREQUENCY DEVIA-TIONS OF A VALVE OSCILLATOR .-Kholo-denko : Berstein. (See 1648 & 1649.)

1628. STABILITY OF OSCILLATIONS IN SYSTEMSOBEYING MATHIEU'S EQUATION.-Brainerd.(See 1646.)

1629. L -R AND C -R SECTIONS ARE DEGENERATEOSCILLATORY CIRCUITS.-E. de Gruyter.(Bull. Assoc. suisse des Elec., 14th' Jan. 1942,Vol. 33, No. I, pp. 19-22 : in German.)

" These considerations form an appendix to myseries of articles on the oscillatory circuit. The lastarticle appeared in this journal in the issue No. 21of 1941, in whose bibliography the other articles canbe found [see 1840 & 4333 of 1939 and 333 of 1941].It is shown that the ' resistance -reactance com-bination ' is the concept which covers oscillatorycircuits, L R elements, and C R elements, asregards impedance and phase. The fact that thereactance may be purely inductive, purely capaci-tive, or mixed, plays in principle no role in therepresentation of this concept, The effectivefrequency ' and the ' zone of influence ' of thecircuits considered are defined in terms of the' time constant.' Finally, a representation is givenof the frequency characteristic corresponding tothe physiology of the human ear, together with anindication of some technical applications."

1630. SERIES -RESONANCE CIRCUIT, COUPLED CIR-CUITS, AND BAND -FILTERS : C ORRECT IONS.-E. de Gruyter. (Bull. Assoc. suisse des Elec.,21st NOV. 1941, Vol. 32, No. 23, p. 622.)Corrections to the last article, in No. 21,mentioned in the above abstract, 1629.

263

-1631. ON THE TEMPERATURE COEFFICIENT OF THEEQUIVALENT -CIRCUIT CONSTANTS IN QUARTZCRYSTAL VIBRATORS FOR ELECTRICAL WAVE -FILTERS . -Z . Kamayachi & T. Ishikawa.(Electrotech. Journ. [Tokyo], Feb. 1941, Vol.5, No. 2, p. 35.)

" Few exact values for (1/d11) . (bd-/bT) havebeen published. However, as it can be imaginedthat it has a negative value in the neighbourhoodof the ordinary temperature, it must be safe to sayfrom eqns. 5 & 6 that values of L and C varyrespectively in opposite directions by the variationof temperature in this vibrator. The results of theauthors' experiments agree with this conclusion,and these coefficients have been found to have largevalues of the order of one thousandth . . . Avibrator having a low temperature coefficient offrequency has not always low temperature coeffi-cient of constants L and C . , . "

1632. A QUARTZ PLATE WITH COUPLED LIQUIDCOLUMN AS A VARIABLE RESONATOR.-FOX& Rock. (See 1756.)

1633. A NEW PRINCIPLE FOR STABLE X)IRECT-CURRENT AMPLIFICATION [for Process Con-trol & Many Other Purposes].-R. Eberhardt,G. Ntisslein, & H. Rupp. (Arch. f. Elektrot.,30th Sept. 1941, Vol. 35, No. 8, pp. 477-489.)

Theoretical treatment of the problem dealt within 3588 of 1941. Authors' summary :-" After ashort survey of the previous development of d.c.amplifiers for measuring purposes, leading to -dayto the photocell -compensator [loc. cit : see alsoBleckwenn, 1133 of April], the paper discusses thefundamental consideratiOns concerning opposed -coupling [negative -feedback] d.c. amplifiers. Twomain types are dealt with, the voltage amplifier andthe current amplifier. By a very high opposed -coupling factor a compensation ' of the quantityunder measurement at the input terminals isobtained. By this compensation the input resist-ance is considerably increased, in the voltageamplifier, and decreased, in the current amplifier.The output resistance providing the negativefeedback can be made either very small or verylarge by the choice of a suitable connection, accord-ing to whether the output is required to deliver aconstant voltage or a constant current. Thevoltage or current amplification factor can be madeas constant as desired by choosing a sufficientlyhigh opposed -coupling factor.

" Formulae for the power amplification with andwithout opposed coupling are derived. Interferingvoltages penetrating anywhere in an opposed -coupling amplifier are reduced more and more intheir effect on the indicating instrument, thegreater the amount of amplification in front oftheir point of entry. In a subsequent second part,practical results with such amplifiers will bereported."

1634. OPTIMUM CONDITIONS FOR MAXIMUM POWERIN CLASS A AMPLIFIERS [Four Cases, givingR = r, R = 2r2,, R = 2or, (Fixed QuiescentPlate Dissipation), & R = 8r, (QuiescentPlate Voltage & Dissipation both Fixed)].-W. B. Nottingham. (Proc. I.R.E., Dec. 1941,Vol. 29, No. 12, pp. 620-623.)


1635. THE ABSOLUTE SENSITIVITY OF RADIORECEIVERS [and the Rating & Measurementof Noise].-North. (See 1656.)

1636. ON THE CORPUSCULAR TREATMENT OF THETHERMAL NOISE OF ELECTRICAL RESIST-ANCES.-E. Spenke. (Wiss. VerOff. a. d.Siemens-Werken, No. 2, Vol. 18, 1939, pp.54-72.)

Bernamont (1715 of 1937) investigated the ele-mentary processes underlying this noise effect,seeing as its cause the individual current pulsesproduced by the random to-and-fro motions of theconduction electrons, and showing that from thisviewpoint also the Nyquist formula could be ob-tained. " The present work has for its first taskthe carrying through of the corpuscular treatmentof thermal resistance -noise by more primitivemathematical methods [based on Fourier analysisof the independent single process] than those ofBernamont, perhaps at the cost of the strictestmathematical rigour. Further, the path -timeeffects of the electrons are taken into consideration.It is found that the ohmic resistance has the samevariation with frequency as the mean square of theeffective voltage value (` Rauschquadrat '), so that .

by employing the resistance value for the particularfrequency in question the formula for the mean' Rauschquadrat ' retains its form even for highfrequencies, whereas if the resistance value forzero frequency is used a frequency -dependent factormust be introduced : for the case of a Maxwellianvelocity -distribution and mean free -path -lengthsindependent of velocity this factor has the valuegiven by Bakker [in his 1938 U.R.S.I. paper,ref. " 5 "]. Finally, some difficulties are discussedwhich occur if the free path of an electron is con-sidered as an independent elementary act."

In a final footnote the writer discusses the con-temporary paper by Bakker & Heller (1842 of1939) in which these workers give the derivationof the frequency formula for the mean " Rausch-quadrat," only stated without derivation inBakker's previous paper : using for this purposean equation (involving a " correlation function ")given by Ornstein & Uhlenbeck : no reference isgiven here but the paper is presumably that re-ferred to in 1931 Abstracts, p. 167, 1-h column. Inthis way, the present writer points out, one of thedifficulties which he has discussed (concerning theFermi-Dirac and Bose-Einstein statistics) is avoided.On the other hand Bakker & Heller kept through-out their work to the ohmic resistance R(o) forfrequency o, and consequently failed to noticethat by using the R(w) for frequency w the Nyquistformula remains valid at high frequencies, asindicated in Nyquist's original paper from thermo-dynamic reasoning and proved in the presentpaper from corpuscular considerations. Bakker& Heller's adherence to R(o) was prompted byideas of capacitive shunts, but these do not inter-fere with the calculation of the mean square of theeffective value, for reasons given.

1637. LAPLACE TRANSFORMATION AND OPERA-TIONAL CALCULUS.-K. W. Wagner. (Arch.f. Elektrot., 3oth Sept. 1941, Vol. 35, No. 8,pp. 502-506.)

Author's summary :-" In the technical litera-

June, 1942

ture the Laplace transformation is used in twodifferent ways. The one leads to the operatorfunction, well known from its practical applica-tions, the other employs the purely mathematicallydefined image function ' [G. Doetsch, who in his1937 book " showed that switching problems couldbe solved from the theory of thermal conductionand electrical lines by transformation by means ofthe Laplace integral "]. It is shown that bothmethods of calculation possess the same fieldsof application and validity, and that the choicebetween them is purely a matter of convenience.This question is examined from the standpoint oftechnical and physical applications : the resultingviews are overwhelmingly in favour of the use ofthe operator function."1638. A BASIS FOR THE COMPLEX CALCULATION OF

ALTERNATING - CURRENT PROBLEMS. - M.Landolt. (Bull. Assoc. suisse des Elec.,19th Dec. 1941, Vol. 32, No. 25, pp. 721-723 :in German.)

" Harmonic oscillations of the same frequencycan be replaced unequivocally by complex quan-tities. This coordination possibility still exists ifsums and differences occur, but it fails for productsand quotients. In an appendix the writer showshow the relations can be described with the help ofsome fundamental concepts of higher algebra."The subject has already been treated in anotherway by Quade (Deutsche Mathematik, Vol. 2, No.pp. 18-31). For a criticism of a paper by Voigt on" a.c. power in symbolic representation " see ibid.,p. 734, where Voigt replies.1639. THE ALGEBRA OF TWO -TERMINAL NETWORKS

CONSISTING EXCLUSIVELY OF TWO -POLECIRCUITS.-V. I. Shestakov. (Journ. ofTech. Phys. [in Russian], No. 6, Vol. 11,1941, pp. 532-549.)

This is an extract from a larger work by theauthor in which it was shown that there is a simpleand mutual relationship between A -networks,i.e. networks consisting exclusively of two -terminalcircuits, and A -formulae, i.e. formulae whoseterms are symbols of the component two -terminalcircuits. These terms are related to each other bytwo mathematical operations only, addition andharmonic addition. It is, therefore, possible towrite down an A -formula for any given A -network,and conversely to build up an A -network corre-sponding to a given A -formula. It is also possibleto derive the required modification of an A -net-work by purely mathematical operations. Thepresent paper is confined to a discussion of thealgebraic properties of A -networks. It is alsoshown that Bul's [presumably Boole, the Irishmathematician] algebra is applicable in the caseof " degenerate " A -networks, i.e. networks ofconductivity equal to o or m. Thug in designingrelay circuits operating from a given combinationof impulses full use can be made of Boole's algebra.Boole's methods are apparently those used byPiesch in the papers referred to in 810 and 967 of1940 ; they are also dealt with in a Russian bookon probability theory.1640. NON - LINEAR DISTORTIONS OF SEVERAL

SINUSOIDAL OSCILLATIONS IN IRON [New'Method of Treatment giving Calculations

I


as Simple as Those for Valves, Rectifiers,& Similar Non -Linear Elements withoutHysteresis : Application to Multiple Tele-graphy, etc.].-F. Strecker. (E.N.T., Oct.1941, Vol. 18, No. Io, pp. 226-238.)

1641. THE GRAPHICAL DETERMINATION OF THE RE-SULTANT RESISTANCE OF SEVERAL PARALLELRESISTANCES [or Resultant Capacitance ofSeveral Cohdensers in Series].-E. Koplin.

3oth Jan. 1941, Vol. 62, No. 5, p. 99,)

TRANSMISSION

1642. A TENTATIVE PROPOSITION ON THE MECH-ANISM OF ELECTRONIC OSCILLATIONS [Pre-fatory Report on a General Investigationtaking Secondary Electrons & Space Chargeinto Consideration : the Formulation of aSimple Ideal Oscillator Valve which, mutatismutandis, represents " Osaka " Valve (925of 1937), Farnsworth Secondary -EmissionOscillator, Heil Tube, Klystron, & B -KOscillator : Some Deductions].-S. Asai.(Electrotech. Journ. [Tokyo], March 1941,Vol. 5, No. 3, pp. 59-60.)

1643. ON SPACE -CHARGE EFFECTS IN VELOCITY -MODULATED ELECTRON BEAMS [Criticismof Webster's Assumptions : Formulation ofTwo Mathematical Models taking Effect ofSpace Charge into Account, (i) for Discussionof Working of V.M. Tubes as H.F. Amplifiers,and (ii) " Domain " Model to give SimpleAnalysis of " Bunching "].-W. H. J.Fuchs & R. Kompfner. (Proc. Phys. Soc.,1st March 1942, Vol. 54, Part 2, No. 302, pp.135-150.)

(i) Below a certain critical length the beam canoperate in the same manner as a beam of particleson which no space charge is acting : the chiefeffect of space charge is an increase in the meantransit time : formulae valid for no space chargerepresent good first approximations if T' = 1100 isreplaced by the actual mean transit time T. Abovethe critical length, the space charge prevents theformation of a continuous beam. (ii) There willbe overtaking and proper bunching, with attendantsplit -bunching, when the current density is belowa critical value : above this value there will be noproper bunching, only " compression," the mutualrepulsion of electrons preventing any overtaking :if the current density is taken too high, the currentpeaks will become low and flat.

Ramo's " electronic wave theory " (1378 of1940) is mentioned as much superior to the ele-mentary theory here developed, in so far as it takesaccount of the finite cross section and the influenceof the screening boundary of the drift space. Buthis boundary conditions (infinite length of beam,variation of electron velocity with distance fromaxis) are not satisfied in reality, so that the resultscan only be regarded as qualitative. " Since ourdiscussion of velocity -modulated beams is physicallymore intuitive and mathematically simpler thanRamo's, we hope that the publication of the presentpaper may still serve a useful purpose."

265

1644. A STABILISED FREQUENCY - MODULATIONSYSTEM [with Centre Frequency directlycontrolled by Single Crystal: DistortionCorrection permitting Large Angles of PhaseShift at Phase Modulator, with Low Dis-tortion, resulting in Simpler Apparatus andReduction of Noise].-R. J. Pieracci. (Proc.I.R.E., Feb. 1942, Vol. 3o, No. 2, pp. 76-80.)

1645. THE R.C.A. IO-KILOWATT FREQUENCY -MODULATED TRANSMITTER.-E. S. Winlund& C. S. Perry. (Proc. I.R.E., Dec. 1941,Vol. 29, No. 12, p. 667: summary only.)

1646. STABILITY OF OSCILLATIONS IN SYSTEMSOBEYING MATHIEU'S EQUATION.- J. G.Brainerd. (Journ. Franklin Inst., Feb. 1942,Vol. 233, No. 2, pp. 135-142.)

" Equation 2 [d2y/dt2 E(I k cos t)y = o] oc-curs in studies of modulation (Carson, Proc.I.R.E., Vol. Io, 1922 [not 1932 as given] : Brainerd,2959 of 194o), in circuit problems such as the oneoutlined above [linear varying -parameter system],and in many non -electrical problems of technicalimportance.. It is thus desirable for practicalpurposes to have the solution of (2) at hand forvarious e, k pairs. At the present time suchsolutions are not available, but a gradual approachto their attainment is being made (617 of 1941).The purpose of this paper is to present curves whichwill facilitate the obtaining of these solutions bygiving values of the characteristic exponentdefined below. These curves serve both to delimitthe stable and unstable states and to giveµ for awide range of the stable state."1647. THE MODULATION AND DEMODULATION

METHOD USING THE CONDENSERS OF PERIOD-ICALLY VARYING CAPACITY [with Applica-tions to Remote Measurement' & SecretCommunication : Analysis].-T. Tomituka.(Electrot. Journ. [Tokyo], March 1941, Vol. 5,No. 3, 131) 43-44.)

1648. ON THE COUPLED OSCILLATIONS OF A HAR-MONIC OSCILLATING CIRCUIT AND A GENE-RATOR OF DISCONTINUOUS OSCILLATIONS.-A. P. Kholodenko. (Journ. of Tech. Phys.[in Russian], No. 4, Vol. II, 1941, pp. 277-301.)

A short survey of the literature on the subjectis given and a theory of the operation of such asystem is proposed. The discussion is confined tosystems satisfying certain conditions, of which themost important are that the harmonic oscillatingcircuit should have a very low damping and thatits natural frequency should not differ appreciablyfrom the natural frequency, or a harmonic, of thegenerator of discontinuous oscillations. As anexample of such systems a dynatron oscillator Dcoupled to a parallel resonant circuit 2 (Fig. 1) isconsidered in detail. The coupling between thetwo circuits is effected through a mutual inductanceM. and an amplifier A. The grid circuit of theamplifier is inductively coupled to the resonantcircuit, while its anode circuit is resistance -coupledto the anode circuit of oscillator D. Equations(43) and (44) determining the operation of thesystem are derived, as well as shortened equations(63) and (64.) The stationary states of the system


corresponding to the appearance of stable oscillationsare investigated, and the amplitude, frequency,and stability of the oscillations are determined.The effect of the parameters of the system onthe amplitude and frequency of the oscillationsis discussed. The operation of the system prior tothe appearance of stable oscillations (nonistationarystates) is also examined. Brief reference is made toother systems (Figs. 12 and 13) to which the theoryexpounded in the present paper is not applicable,and the paper ends with a report on experimentsto verify the theoretical conclusions reached.

1649. THE FLUCTUATIONS IN AUTO -OSCILLATINGSYSTEMS AND THE DETERMINATION OF THEFREQUENCY DEVIATIONS OF A VALVE OSCIL-LATOR.-I. L. Bershteyn [Berstein]. (Journ.of Tech. Phys. [in Russian], No. 4, Vol. II,1941, pp. 305-316.)

The fluctuations in an oscillating system of theThomson type due to momentary casual changesin the parameters of the system are considered.The dynamic equations of the system (1 and 2) arewritten down and analysed, using the van der Polmethod. The corresponding Einstein-Pokker equa-tion (i8) is also derived: The cases of " isotropic "and " non -isotropic " fluctuations are consideredseparately, and for each case methods are indicatedfor determining the width of the frequency bandgenerated by the system, as well as the amplitudeand phase fluctuations. The purely mathematicaldiscussion is illustrated by considering a physicalcircuit, a valve oscillator with the tuned circuitconnected in the anode circuit (Fig. I). Thepossibility of an experimental verification of thetheory is also discussed and indicated.1650. VARIABLE - FREQUENCY BRIDGE - STABILISED

OSCILLATORS [incorporating Thermal Devicefor Amplitude Control].-W. G. Shepherd &R. 0. Wise. (Proc. I.R.E., Dec. 1941,Vol. 29, No. 12, p. 666: summary only.)

1651. A NEW AIR-COOLED 5 -KILOWATT BROADCASTTRANSMITTER [Westinghouse] .-F.W. Fischer.(Proc. I.R.E., Feb. 1942, Vol. 3o, No. 2,p13-72-75-)

RECEPTION

1652. SIMULTANEOUS AURAL AND PANORAMIC RE-CEPTION .-Wallace . (See 1702.)

1653. THE AUTOMATIC TUNING OF AMPLIFYINGSTAGES [where Incoming Frequency mayVary over Wide Ranges, as in Distance -Determining Technique].-Yuzvinski. (See1703.)

1654. COMMON -CHANNEL INTERFERENCE BETWEENTwo FREQUENCY - MODULATED SIGNALS[Analysis, with Results which have beenVerified by Tests].-H. A. Wheeler. (Proc.I.R.E., Jan. 1942, Vol. 3o, No. 1, pp. 34-50.)

Subdivision into frequency and amplitudeeffects : beat -note interference cannot be reducedmuch by avoiding amplitude effects, can be reducedby using band -width of f.m. exceeding twice thatrequired by modulating signal: cross -talk inter-ference (amplitude effect) minimised by limiter, its

June, 1942

amplitude from linear rectifiers only half that fromsquare -law : use of " conical patterns " for testsetc. For94LFor previous work on f.m. see 1876 & 3297

1655. AN ANALYSIS OF THE SIGNAL/NOISE RATIOOF ULTRA -HIGH -FREQUENCY RECEIVERS.-E. W. Herold. (Proc. I.R.E., Dec. 1941,Vol. 29, No. 12, p. 665: summary only.)

Ratio depends on antenna noise, on equiv. noise-resistance/input-resistance of first valve (whenband -width is not a consideration) and on input -capacitance x equiv. noise -resistance (when it is amajor consideration) : optimum antenna/first-valvecoupling (often considerably different from adjust-ment for max. gain) : thermal noise from wide -band inter -stage circuit made negligible by con-centrating all the damping on secondary side : etc.

1656. THE ABSOLUTE SENSITIVITY OF RADIORECEIVERS [and a Method of Rating &Measuring the Noise in Complete ReceivingSystems (particularly U.H.F.) includingAerials : Study of Receiving Aerials, yieldingAlternative Derivation of Nyquist'sTheorem].-D. 0. North. (Proc. I.R.E.,Dec. 1941, Vol. 29, No. 12, p. 665: summaryonly.)

" The total random noise originating in a receiverhas customarily been described in terms of theequiv. noise voltage at the receiver input terminals.A comparison of the signal/noise ratios of tworeceivers working out of identical antennas isthereby facilitated, but only as long as the couplingbetween antenna and receiver input is extremelyloose."

1657. ON THE CORPUSCULAR TREATMENT OF THETHERMAL NOISE OF ELECTRICAL RESIST-ANCES.-Spenke. (See 1636.)

1658. THE, DETECTION OF A CONTINUOUS SPEC-TRUM.-I. L. Bershteyn [Berstein]. (Journ.of Tech. Phys. [in Russian], No. 4, Vol. i1,1941, pp. 302-304.)

A mathematical discussion in which methods areindicated for determining the result of square -lawdetection when a continuous frequency spectrum isapplied to the grid of the valve.

1659. ON THE MEASUREMENT OF HIGH -FREQUENCYINTERFERENCE.-F. Conrad. (E.N.T., June

, 1941, Vol. 18, No. 6, pp. 126-133.)Steudel & Milller's work (1933 Abstracts, pp. 510-

511, and 969 of 1937), which is briefly discussedhere, has done much to solve the problem of the1.f. portion of a h.f. interference measuring ap-paratus, but leaves a number of questions to beanswered regarding the h.f. side. Two difficultiesin particular remain : first, the curve form of h.f.interference is in general unknown, both thatdirectly at the source and that after conductionalong lines or after radiation : such determinationshave not been made so far and would be difficult,and yet the knowledge is needed in order to be ableto say at what amplitudes a measuring equipmentwill still act correctly. Secondly, various observa-tions on h.f. receivers working close to interferingsources have shown that oscillations in the ultra -short or even in the decimetric-wave region may


appear from any ordinary source and will, unlessthe apparatus is adequately shielded, upset themeasurements.

A measuring device with which repeatable h.f.interference amplitudes can be measured withregard to their noise -level after demodulation mustto all intents be identical, right up to the rectifier,with a standard receiver. The whole equipmentmust therefore consist of a h.f. voltage divider withas high an ohmic input resistance as possible, ah.f. amplifier, rectifier, and sound -level indicator.The writer discusses the question of receiver band-width, the use of " straight " or superheterodynecircuits (the latter have the advantage of a constantband -width, but require steps to be taken to cutout image -frequencies), and the rectifier charac-teristic. With regard to the latter, it is seen thatthere can be no proportionality between theamplitudes at the grid of the input valve and theindications of the noise -level instrument, if therectifier is over -controlled. This means that auto-matic recording of uncontrolled interference (e.g.from power mains or atmospherics) is only possibleto a limited extent. This difficulty is perhaps bestdealt with by controlling the h.f. input so that thedeflection of the noise -level meter is kept constant.Further consideration shows also that it is practicallyimpossible to get consistent results with differentequipments unless these are electrically and electro-acoustically identical in all their parts ; exceptperhaps in the case of continuous interference suchas glow -discharge or commutator noise. Variousother points are discussed, and a fundamentallay -out of an equipment is given in Fig. 5, withoutany details whatever. It is stated that a numberof problems discussed in a previous paper (1934Abstracts, p. 38o) have been solved in the mean-time, but the one relating to wave -form remainsunsolved.1660. OFFICIAL PRODUCTION OF A PORTABLE

INTERFERING -VOLTAGE MEASURING APPAR-ATUS [to check that ASE-UCS Limit ofI my for Low -Power Machines & Appliancesis Not Exceeded].-(Bull. Assoc. suisse desElec., 29th Aug. 1941, Vol. 32, No. 17, p.424.) For a further note see No. 24 (5thDec. 1941), p. 678.

1661. A NOTE ON THE SOURCES OF SPURIOUSRADIATIONS IN THE FIELD OF TWO STRONGSIGNALS [resulting from Non-Linearities inConductors which serve as Antennas :Special Susceptibility of A.C. Receiverwhich is Not Earthed (" Electrical -Distribu-tion -System Grounds are Notorious forRectification ") : Methods of Reduction :etc.].-A. J. Ebel. (Proc. I.R.E., Feb. 1942,Vol. 3o, No. 2, pp. 81-84.) See also 1029of April.

1662. AIRCRAFT PRECIPITATION -STATIC RADIO IN-TERFERENCE.-Starr. (Jowl/. Roy. Aeron.Soc., April 1942, Vol. 46, No. 376, pp. 127-'28 : summary only.)

WHISTLING METEORS : A DOPPLER EFFECTPRODUCED BY METEORS ENTERING THEIONOSPHERE [Weak Heterodyne Whistlesof Unusual Type in Short -Wave Reception].-Lal & Venkataraman. (See 1607.)

1663.

1664.

267

METHODS OF H.F. INTERFERENCE SUP-PRESSION FOR MACHINES AND APPLIANCESUP TO 500 WATTS [General Principles(Symmetrical & Asymmetrical InterferenceVoltages)

Condenser Connections : Con-denser Requirements (including the " Cord "Condenser) : Practical Examples].-K. Kegel.(AEG Mitteilungen, Sept./,Oct. 1941, No. 9/1o,pp. 238-244.)

1665. ELECTRICAL INTERFERENCE TO BROADCASTRECEPTION [in India : Special Conditionsdue to Wide -Spread Use of Ceiling Fans,Pumps, Refrigerators, etc., chiefly on D.C:Specially Developed Method of InterferenceMeasurement : Effects of Speed Regulation :Polarisation of Interference Signals : Signal/Total -Noise Ratio on Various Wave -Bands :etc.].-S. P. Chakravarti & N. L. Dutt.(Indian Journ. of Phys., Oct. 1941, Vol. 15,Part 5, pp. 365-387.)

1666. ON THE FADING REDUCTION IN THE SPACEDIVERSITY RECEPTION [Improvement Factorfound to be proportional to about .N1-4 andto Logarithm of n : Improvement Factoron Optimum (Least Attenuated) Frequency,for Given Distance, is Smaller as Frequencyis Higher].-M. Nakagami & others. (Elec-

,

trotech. Journ. [Tokyo], Feb. 1941, Vol. 5,No. 2, pp. 36-37.) Where N is the fadingratio for one aerial and n is the number ofaerials.

1667. SOME OBSERVATIONS ON SPACE DIVERSITYEFFECT BY PHOTOMETRY [for obtainingthe Statistical Characteristicsfrom Two Aerials (after Amplification &Logarithmic Compression) led to Two Setsof C.R.O. Deflecting Plates : Movement ofBright Spots photographed and Densityon Film . measured Photometrically : SomeResults : even with Spacing of only OneWavelength, Fading does Not necessarilySynchronise]. - M. Nakagami & others.(Electrotech. Journ. [Tokyo], Feb. 1941,Vol. 5, No. 2, p. 39.)

1668. THE OPERATION OF FREQUENCY CONVERTERSAND MIXERS FOR SUPERHETERODYNE RE-CEPTION.-Herold. (See 169o.)

1669. SUPERHETERODYNE TRACKING CHARTS: II.-Ruby Payne -Scott & A. L. Green.(A.W.A. Tech. Review, Dec. 1941, Vol. 5,No. 6, pp. 251-274.)

In Part I (87 of January) it was assumed, forsimplification, that the capacitance in shunt withthe oscillator coil was negligibly small ; in thepresent paper the problem of the distribution ofstray and trimming capacitances in the oscillatorcircuit is considered " and is found to lead to someinteresting conclusions." Part I is reprinted in thisissue of Wireless Engineer, and Part II will appearin July.1670. STANDARD TESTS ON BROAD CAST RECEIVERS

[based on R.M.A. 1936 Standards & I.R.E.1938 Standards].-V. V. L. Rao. (Electro-technics [Bangalore], Nov. 1941, No. 14,PP. 40-49.)


1671. THE SWISS RADIO EXHIBITION AT ZURICH[Glass -Base Valves : Push -Button Tuning(chiefly without Motor Drive or A.T.C.) :Automatic Selectivity Control: Economyin Materials : Interference Reduction bySpecial Aerial : etc.].-(Bull. Assoc. suissedes Elec., 12th Sept. 1941, Vol. 32, No. 18,PP. 443-444.)

1672. TROPICAL CLIMATE AND COMMUNICATIONTECHNIQUE [with Data (Temperature,Humidity, etc.) for Various Tropical Re-gions : Insulation Troubles : Damage byDust Storms, Insects : etc.].-W. M. H.Schulze. (E.N.T., June 1941, Vol. 18,No. 6, pp. 134-147.) A shortened versionwill appear in the July Wireless Engineer.

1673. SOME ASPECTS OF THE IMPACT OF WARECONOMY ON CIVILIAN RADIO [Symposium].

1674.

-L. C. F. Horle & others. (Proc. I.R.E.,NOV. 1941, Vol. 29, No. II, p. 603: sum -manes only.)

CIVILIAN RECEIVER DESIGN IN 1942 [andthe Place of the Minimum of 7- MillionBroadcast Receivers in the Defence Pro-gramme, for the Morale -Building Propa-ganda Machine : Necessary , Standardisa-tion, Materials Substitution, Cooperation,etc.].-D. D. Israel. (Proc. I.R.E., Dec.1941, Vol. 29, No. 12, pp. 649-653.)

AERIALS AND AERIAL SYSTEMS

1675. RADIATING SYSTEM FOR 75 -MEGACYCLE CONE -OF -SILENCE MARKER [for Canadian Airways :with Sharper Vertical Beam and SmallerOrientation Effect].-E. A. Laport & J. B.Knox. (Proc. I.R.E., Jan. 1942, Vol. 3o,No. 1, pp. 26-29.)

1676. ELLIPTIC AND SPHEROIDAL WAVE FUNC-TIONS.-ChU & Stratton. (See 1594.)

1677. RADIATION ENERGY AND EARTH ABSORP-TION WITH DIPOLE AERIALS.-A. Sommer-feld & F. Renner. (Ann. der Phys., Feb.1942, Vol. 41, No. r, pp. 1-36.)

" In text -book literature, which agrees mainlywith the Hertz-Zenneck formula, this influencingof the radiation resistance by the ground and bythe position of the aerial with respect to this isnot spoken of. We consider, therefore, thatthe elucidation of these points forms the principalresult of our work." A full translation is beingprepared for immediate publication in WirelessEngineer.

1678. THE MAYERL PROCESS FOR THE IMPREGNA-TION OF WOODEN MASTS [in Position].-V. Friesz. (E.T.Z., I2th Feb. 1942, Vol. 63,No. 5/6, pp. 73-74 : summary only.)

1679. " DER LEITUNGSMAST AUS HOLZ . . . [TheWooden Overhead -Line Mast : Its Material,Its Animal & Vegetable Destroyers, ItsImpregnation & Maintenance : Book Re-view].-B. Fenske. (Bull. Assoc. suisse desElec., 19th Dec. 1941, Vol. 32, No. 25, p. 737.)

June, 1942

VALVES AND THERMIONICS

1680. SPACE - CHARGE RELATIONS IN THE MAG-NETRON WITH PLANE ELECTRODES.-E. A.Condon. (Proc. I.R.E., Dec. 1941, Vol. 29,No. 12, p. 664: short summary only.)

1681. THEORY OF THE MAGNETRON [Study of Mag-netron in Static Condition, with StrictRegard to Influence of Space Charge].-L. Brillouin. (Elec. Communication, No. 2,Vol. 20, 1941, pp. 112-121.) Paper preparedin -Jan. 1939 : for a later work see 107 ofJanuary.

1682. THE DESIGN AND DEVELOPMENT OF THREENEW ULTRA -HIGH -FREQUENCY TRANSMIT-TING TUBES [including Precautions forSatisfactory Operation]. - C. E. Haller.(Proc. I.R.E., Jan. 1942, Vol. 3o, No.pp. 20-26.) A summary was referred to inio6o of April.

1683. ON SPACE -CHARGE EFFECTS IN VELOCITY -MODULATED ELECTRON BEAMS.-Fuchs &Kompfner. (See 1643.)

1684. THE EFFECT OF SPACE CHARGE ON THEPOTENTIAL AND ELECTRON PATHS OF ELEC-TRON BEAMS [More Important Results ofAnalyses collected from Literature andpresented in Curves & Nomograms forPractical Application : Diodes, Tetrodes,Long Flat Beam, Cylindrical Beam].-D. P. R. Petrie. (Elec. Communication, No. 2,Vol. 20, 1941, pp.

1685. ON THE THEORY OF ELECTRON -PLASMA

Phys., ist Feb. 1942, Vol. 118, No. 9/io,pp. 618-623.)

Author's summary :-" It is shown how theLangmuir oscillation -equation for the plasmaelectrons can be arrived at by a combination of thepotential equation and the equation of motioneither with the continuity equation of electronflow [" hydrodynamic " treatment: bnOt b(nv)Ibx= o] or with the equation for the total currentmade up of the displacement and convectioncurrents [" electrical " treatment : J = (1/47r) . M/bt+ env] : how these two ways of treating theproblem are interconnected : and that they arecompletely equivalent." The difference betweenthe problem here considered and that dealt withby Schumann (2685 of 1941), which also involvesthe Langmuir frequency 4ire2nolm, is pointed outin §4 : this section also calls attention to the factthat the transit -time theory of electron flow can,in an analogous way, be developed either on hydro-dynamic or on electrical lines : an example of theformer is provided by Benham's work (1928Abstracts, p. 288), of the latter by Muller's papers,1933 Abstracts, pp. 443-444, and 502 of1936.1686. ON THE DIELECTRIC CONSTANTS OF IONISED

GASES AT MEDIUM RADIO-FREQUENCY.-Khastgir & ,Choudhury. (See 1599.)

1687 THEORY OF THE VARIATION OF THE RESIST-ANCE OF A THERMIONIC VALVE WITH FRE-QUENCY.-S. R. Khastgir. (Indian Journ. ofPhys., Oct. 1941, Vol. 15, Part 5, pp. 317-321.)

For a shortened version see Sci. 6, Culture, May

1


1941, Vol. 6, No. II, pp. 671-672. Mitra & Sildeveloped a theory of this variation (1932 Abstracts,p. 463) and showed that their experimental resultswere entirely at variance with Hartshorn's theory(1931 Abstracts, p. 618). Rao (93 of 1941) extendedthe frequencies downwards and found that thedecrease in resistance with decreasing frequency,found by Mitra & Sil, changed to a gradual increaseat the lower frequencies now used. " This latterresult, which has also been recently confirmed by adifferent method[see Basak, 1688, below], cannotbe explained according to Mitra & Sil's theory,"according to which the resistance should be constantbelow a certain limiting frequency. The presentwriter accepts their fundamental ideas regardingthe conductivity due to convection current, buttakes into account that arising from the displace-ment currents. He finds that ad, the specificconductivity due to these currents, is equal toe(0/4.7r. " It was shown by Khastgir & Choudhury(92 of 1941 : for an extension see 1599, above) thatthe value of (1 - e) varied inversely as the squareof frequency. Even if e were regarded as constant,ad would steadily increase with the increase offrequency," while the conductivity due to theconvection current, as soon as the frequency exceedsthe limiting value defined by eqn. 3, would no longerremain constant but would begin to decreasesteadily with further increase of frequency. " Theexperimental results on the conductivity of a valvefor a wide range of frequencies can therefore beexplained."

Rao's tests on a Telefunken valve gave the turningpoint at a wavelength of about i8o m, muchlonger than the value of 30-45 m to be expectedfrom eqn. 3. " The equation e0/3oo = imuo2,from which eqn. 3 is derived, is however based onclassical ideas. The results should be reviewed inthe light of modern views of electron emission frommetals."

1688. ON THE HIGH -FREQUENCY CONDUCTIVITYAND EFFECTIVE DIELECTRIC CONSTANT OFELECTRONIC MEDIUM IN A HIGH -VACUUMTHERMIONIC VALVE lin the Medium Fre-quency Band].-R. G. Basak. (IndianJourn. of Phys., Oct. 1941, Vol. 15, Part 5,PP. 343-358)

An investigation of the anode/screen-grid spacein a Philips B442 valve, with a view to estimatingthe merits of the theories put forward by Benner(1930 Abstracts, p. 152), Hollmann & Thoma(" inversion " theory : 3840 of 1938), and Mitra &Sil (1932 Abstracts, p. 463). The first set ofmeasurements, at two different frequencies, gave alinear relation between conductivity and electronconcentration : this would be expected from anyof the theories. The second set gave a conduc-tivity, for a fixed thermionic current, increasing asthe frequency was increased over the range inquestion, 512 kc/s to i000 kc/s (agreeing withRao's results : see Khastgir, 1687, above). Thethird set (Fig. 5), with thermionic current main-tained constant while the anode voltage was varied,showed a very rapid increase in conductivity, for afixed frequency, with increasing time of stay of theelectrons. The first result, though qualitativelyconforming with either Benner's or Hollmann &

269

Thoma's theory, gives by either theory quiteunsuitable values for the electron concentration.The second result is contrary to Benner's theoryand when combined with Rao's results is contraryalso to Hollmann & Thoma's theory. The thirdresult showed an observed increase in conductivitywhich was too rapid for either theory. Khastgir'stheory (loc. cit.) is therefore adopted.

As regards the effective dielectric constant,previous experiments have -shown that bothBenner's and Hollmann & Thoma's expressions areuntenable (456 of 1940 and 92 of 194.1). In thesepapers a multiplying factor µ = (A IA) . f (T) wasintroduced into the Lorentz formula for the dielec-tric constant of a frictionless electronic medium, toallow for the effect of the time of stay of theelectrons in the interelectrode space : it was shownthat p. was independent of A /A and depended onlyon the time of transit. The experiments nowdescribed were to find the nature of this dependence.It was found that until the anode voltage wasraised above the point where secondary emissionoccurred, the effective dielectric constant increasedas the voltage increased : that is, it decreased asthe time of stay was increased. It is thereforeconcluded that in the modified Lorentz formula

- 41r(Np.)e2/91(.02, must increase with theincrease of the transit time T.1689. OPTIMUM CONDITIONS FOR MAXIMUM POWER

IN CLASS A AMPLIFIERS.-Nottingham. (See1634.)

1690. THE OPERATION OF FREQUENCY CONVERTERSAND MIXERS FOR SUPERHETERODYNE RE-CEPTION [General Analysis of Operationcommon to All Types (including FluctuationNoise) : Comparison of Advantages & Dis-advantages of Three Conversion Methods :Improved Constructions for Mixers designedfor Outer -Grid Injection : etc.].-E. W.Herold. (Proc. I.R.E., Feb. 1942, Vol. 3o,No. 2, pp. 84-102.)

1691. THE CHOICE OF VALVES FOR MODERNTECHNICAL AMPLIFIERS [for Studio Purposes,etc : Doubtful Validity, nowadays, of theIdea that only " Technical " Valves, withCloser Tolerances than Usual Broadcast -Receiver Valves, are Permissible : Com-parison of AC too & Ca " Technical " Typeswith the E Series, such as the EF 12, ofBroadcast -Receiver Valves].-W. Schlecht-weg. (E.N.T., Oct. 1941, Vol. 18, No. lo,pp. 219-221.)

1692. AMPLIFICATION BY SECONDARY -ELECTRONEMISSION IN STATIC MULTIPLIERS.-H.Schnitger. (E.T.Z., 29th Jan. 1942, Vol. 63,No. 3/4, pp. 41-46.)

The silver-oxide/caesium films almost exclusivelyused to -day in photomultipliers have the advantageof good secondary emission (for 400 v primaryvoltage, nine secondaries for each primary), butthey are quickly destroyed by temperatures aroundzoo° C and are therefore unsuitable for multiplierswith anything approaching a large output. Thesearch for better secondary -emission layers has 'led,so far, to the development of layers of magnesiumoxide (4456 [and 549] of 1939 : 2718 of 1941) and


of oxidised beryllium alloys (reference " 2," and2135 & 2717 of 1941), both of which will stand5oo°C and over. The usefulness of the ratio u/pfor comparing the merits of such layers is explainedand illustrated by a comparison of the magnesium-.oxide and silver-oxide/caesium layers : see longabstract, 451 of February.

Section 2 deals with different types of multiplierfrom the electron -optical viewpoint : specialattention is given to the Weiss " net " multiplier,and to the high efficiency (nearly 100%) of theSlepian type with an auxiliary magnetic field(Fig. 3d). The limiting of the permissible output -current strength, both by space charge and thermalloading, is discussed in section 3. Section 4 dealswith background noise : the additional compo-nent due to secondary emission can be calculatedapproximately by the Schottky formula (the paperby Zworykin & others, 2185 of 1936, is here quoted) :the question of how much better, as regards noise,a photomultiplier is ° than a photocell/amplifiercombination, is considered by calculating the small-est permissible photocurrent 10 for the two casesunder similar conditions, for a given height H ofthe signals above the background -noise level anda given modulation depth M : the ratio E of thesecurrents is found to be 3800 MIH, which is inde-pendent of the band width and which gives as atypical value, for H = 8 and M = 0.4, a sensitivityimprovement of about 200 times on using themultiplier. The question as to the optimumnumber of stages is answered by the fact that inthe most favourable case the additional noise dueto the coupling elements in the anode circuit isreduced to practically zero : this occurs when themultiplication reaches about 5E, that is,, 1000(Preisach, 2864 of 1939) : so far as noise is concerneda further increase in stages would improve mattersvery little. In caesium -activated cathodes thedark current ID at room temperatures (which doesnot as a rule interfere with a photocell/amplifiercombination) reduces the smallest permissiblephotocurrent for a multiplier, and thus reducesthe improvement -ratio E : the new ratio E' isgiven by E' = (o.5 -I- 0.5 - 4/D//0), whichwhen the dark current is taken as equal to thesmallest permissible cathode current gives animprovement -ratio of only about 124 instead of 200.

Section 5 deals first with multipliers designedspecially for television, beginning with the " net "type and " zig-zag " types, and passing then tothe magnetic type with specially designed permanentmagnets and soft -iron poles, having the electrodesdeposited on the glass walls (Figs. 7 & 8) : thecomplete magnet for a f o -stage multiplier, with" Magnetoflex " iron -nickel -copper alloy, weighsonly 27o gms. The magnet body serves for variousauxiliary purposes : thus it carries inside thepotentiometer for all except the last stages. Ao -stage multiplier of this type gives a " charac-

teristic voltage " (see 451 of February) of only65 v per' neper ; the max. output current, limitedby space charge and thermal considerations, isabout f MA. The superior stability against supplyfluctuations possessed by the permanent -magnetmultiplier, compared with the electrostatic type, ispointed out and illustrated by the curves of Fig. f o :for a 1% voltage fluctuation the multiplying factor

June, 1942.

alters by only o.8%, compared with 3.4% with amagnet -less type. For large fluctuations (usuallyavoided easily) conditions are better for theelectrostatic type, but the stability of the magnetictype can be improved by making the permanentmagnet provide, say, only 64% of the total field,the remainder being furnished by a field windingsupplied from the electrode -voltage source. A 1%fluctuation then causes a factor variation of only0.1% (curve 3 of Fig. f o). Finally it is mentionedthat for many purposes it is desirable to make theinternal resistance Ri as high as possible in com-parison with the fixed external resistance, to avoidthe distortion due to variations of Ri with the lightflux changes : this high internal resistance isobtained by a separate leading -out of the fieldelectrode in front of the last s.e. electrode, insteadof a direct connection to the anode : it can thus bemaintained at a constant potential.

Section 6 deals with grid -controlled multipliersfor the amplification of wide frequency -bands (2334of 1938 : 1466 of 1939 [use of the initial -currentregion] : and 2415 of 1941 [various methods,including the initial -current region]). This use ofthe initial -current region is discussed : it has greatadvantages as regards steep slope, but it is badfrom the point of view of noise. It is concludedthat the input current of a multiplier should notbe reduced below the point where the curve ofrelative slope (S/I curve) lies in the space -chargeregion. The 3 -stage grid -controlled multiplier ofFig. 12, on these lines, has a slope of 3o mA/v withan output current of I 0 mA and a 12 pF valve -capacitance, so that the ratio SiG, of great import-ance fo'r wide -band amplification, is 2.5, whicha great improvement on the 0.7 normally obtainedwith amplifier valves. The equivalent noise -resistance is 5 kilohms.

1693. THE EFFECT OF THE ANGLE OF EJECTION -ON THE ENERGY DISTRIBUTION OF SECOND-ARY ELECTRONS. - Yu. M. Kushnir &

M. I. Frumin. (Journ. of Tech. Phys [inRussian], No. 4, Vol. II, 1941, pp. 317-322.)

Experiments made with Mo and Ag layers aredescribed and experimental curves shown. Theresults obtained are discussed, and the mainconclusion reached is that with an increase in theangle of ejection (measured from the directionnormal to the surface) the maximum for the energydistribution of secondary electrons moves towardsfaster electrons (Figs. 3-6). It has also beenobserved that the curves showing, the distributionsof electrons for varying angles of ejection have anumber of well-defined maxima and minima. It issuggested that this phenomenon is due to thediffraction effect.1694. THE CRYSTALLOGRAPHIC STRUCTURE OF

ALKALINE -EARTH OXIDE MIXTURES : IN-VESTIGATIONS ON OXIDE CATHODES WITHTHE HELP OF RoNTGEN RAYS AND ELECTRONBEAMS.-H. Huber & S. Wagener. (Zeitschr.f. tech. Phys., No. I, Vol. 23, 1942, pp. 1-12.).

In his 1941 Berlin Dissertation Huber showedthat the thermionic emission from oxide cathodescomposed of various binary mixtures BaO-Sr0,BaO-CaO, and SrO-CaO displayed characteristicdifferences between the BaO-SrO system and the


SrO-CaO system on the one hand and the BaO-CaOsystem on the other. Since Benjamin & Rooksbyhave already reported (1933 Abstracts, p. 569) thatthe emission current from BaO-SrO cathodes isfavourably affected by the formation of mixedcrystals, the crystallographic structure of theother mixed -oxide cathodes ought also to be im-portant with regard to their emitting properties.The present investigation of the structure of thesecathodes should therefore contribute to our know-ledge of -the dependence of emission on the com-position of such cathodes.

Authors' summary :- " The crystallographicstructure of oxide cathodes consisting of binarymixtures of the alkaline -earth oxides BaO, SrO,and CaO is examined. The carbonate mixturesused for the preparation of the oxide mixtures, andobtained by a common precipitation [from nitratesolutions], are shown by Debye-Scherrer photo-graphs to be composed entirely of mixed crystals.It is found by similar means that in accordancewith Grimm's mixing rules [reference " 14 "] theBaO-Sr0 and SrO-CaO mixtures are composed ofmixed crystals, while the BaO-CaO mixturesconsist of a microcrystalline medley [a mixed -crystal formation being possible, according toGrimm, only when the difference in the latticeconstants is not more than ii%].

" Electron -diffraction photographs, taken withthe Seemann apparatus, showed at the surface ofall the oxide mixtures the presence of a layer of theless easily vaporisable component [the othercomponent having been evaporated out of thelayers near the surface by the usual process ofoxide -cathode formation]. The layer thickness isestimated at between 300 and 2000 atomic layers.The significance of the results for the emittingproperties of mixed -oxide cathodes is discussed " :

the fact that the conditions at the surface of the4 cathodes after the activating process are similar

indicates that with the BaO-SrO system, as withthe other systems, the surface alters little instructure or composition over a wide range ofmixtures. Consequently the surface work function,governing the electron emergence, must remainapproximately constant over this range, so that allvariations of emission within this range must beattributed to the influence of the deeper -lying oxide

4 layers, i.e. chiefly to the semiconductor properties.This conclusion is strengthened by the fact that

r the mixed -crystal systems (BaO-SrO and SrO-CaO)show fundamentally similar emission characteristicsplotted against composition, in contrast to theBaO-CaO system with its microcrystalline mixtureof components. This indicates that the semi-

' conductor properties of mixed-oxide cathodes areconsiderably changed by the formation of mixedcrystals, in that the " Ablosearbeit " of the electronsin the interior of the crystals is diminished [vanGeel, 1931 Abstracts, p. 513, uses the term" Ablosearbeit " to denote d W, where W is theSommerfeld internal work function]. " At presentno direct experimental material is available con-cerning such influence, so that nothing definite canbe said about the mechanism."

1695' THE MAGNETIC INDUCTION FIELD OFAIR -CORE COILS AND ITS APPLICATION TO

271

HIGH - FREQUENCYMANUFACTURE.-C.Tech. Review, Dec.292-256.)

Author's summary :-" Expressions are derivedfor the axial components of the magnetic inductionfield of both three-dimensional and two-dimensionalcoils : in particular the Helix, the Spirals rand r = roeke, and the simple Circular Coil areinvestigated. Efficient heating by a h.f. inductionfield, and the design of heater coils such as thoseuse in valve manufacture, are discussed in somedetail."

HEATING IN VALVEB. Kirkpatrick. (A .W.A .

1941, Vol. 5, No. 6, pp.

1696. ADSORPTION PROPERTIES or METALLIC ZIR-CONIUM FOR GASES, AND ITS APPLICATIONSTO ELECTRON TUBES.-S. Hukagawa &J. Nambo. (Electrotech. Journ. [Tokyo],Feb. 1941, Vol. 5, No. z, pp. 27-30.)

The action " is extremely strong against allharmful gases when the Zr is at 400° to 600°C . . .

transmitting tubes of a much smaller size thanheretofore can be made . . . Zr treatment wasalso given to the grids, which was effective indiminishing secondary electron emission . . . aver-age life of some types of tubes was doubled." Canalso be used to purify the gases (neon, etc.) usedin the manufacture of discharge tubes, etc.

DIRECTIONAL WIRELESS

1697. RADIATING SYSTEM FOR 75 -MEGACYCLE CONE -OF -SILENCE MARKER [for Canadian Airways :with Sharper Vertical Beam and SmallerOrientation Effect].-E. A. Laport & J. B.Knox. (Proc. I.R.E., Jan. 1942, Vol. 3o,No. I, pp. 26-29.)

1698. AN ULTRA -HIGH -FREQUENCY TWO -COURSERADIO RANGE WITH SECTOR IDENTIFICA-TION.-A. Alford & A. G. Kandoian. (Proc.I.R.E., Dec. 1941, Vol. 29, No. 12, p. 664:summary only.)

1699. A WIDE -RANGE, LINEAR, UNAMBIGUOUS,DIRECT -READING PHASEMETER [deliveringa Direct Current proportional to PhaseAngle] .-Shepherd . (See 1747.)

1700. FUNDAMENTAL CONSIDERATIONS ON THEELECTRICAL AND ACOUSTICAL MEANS FORAIRCRAFT NAVIGATION IN FOGGY WEATHER.-W. Hahnemann. (Bull. Assoc. suisse desElec., 28th Feb. 1941, Vol. 32, No. 4, pp. 67-68: summary. in German, from Lorenz-Berichte, No. 3/4, 1939, p. 73 onwards.)

Leading to a table showing the relative applica-bility of various waves, electromagnetic and acous-tic, for various types of navigation aid, namelylong-distance, normal -distance, and close hori-zontal d.f. ; vertical location (altitude determina-tion) for great and small heights ; precision guidingfor landing or taking -off ; collision prevention(obstacles) and collision prevention (other aircraft).It is suggested that the cosmic rays (" wavelengthsro-11 to ri-'3cm ") will eventually be useful formeasuring great altitudes, where the barometerfails. Millimetric waves are considered to presentfew possibilities, because like infra -red rays theiradvantage over luminous rays is too small to make

E


the added complications worth while, and moreoverthey do not come back from the ground : they are,however, easy to concentrate. So are the centi-metric waves, and these, recent investigations haveshown, have quite large ranges, up to 5o km : whentransmitting and receiving apparatus has beenimproved they should offer some possibilities.Decimetric waves are suitable for most of the dutiesin question, except when the distances exceed theoptical range : they are well reflected from theground. Metric waves have ranges rather greaterthan the optical : those over 6 m have much greaterranges, thanks to reflection at the ionosphere, andare very suitable for all navigation problems,except (because they are too long to concentratewith small reflectors) collision prevention.1701. DIRECTION FINDING AT MEDIUM -HIGH FRE-

QUENCIES AND THE UNITED AIR LINESGROUND -STATION DIRECTION FINDER.-P. C.Sandretto & E. P. Buckthal. (Proc. I.R.E.,Nov. 1941, Vol. 29, p. 604: summary.)

1702. SIMULTANEOUS AURAL AND PANORAMIC RE-CEPTION [Adaptor permitting UninterruptedVisual Observation of Relatively Wide Bandabove & below Station listened to : ManyApplications].-M. Wallace. (Proc. I.R.E.,Dec. 1941, Vol. 29, No. 12, p. 667: summaryonly.) For previous work on panoramic re-ception see io88 of 1941 and back reference.

1703. THE AUTOMATIC TUNING OF AMPLIFYINGSTAGES [for Distance -Determination Tech-nique, etc.].-V. I. Yuzvinski. (Journ. ofTech. Phys. [in Russian], No. 5, Vol. II, 1941,PP 456-459.)In a number of cases, as for example in deter-

mining distances by the Mandelstam-Papaleximethod (see 836.8c 3103 of 1938, 3176 of 1939, and622/627 of March and back references), the fre-quency of the received e.m.f. may vary within widelimits. At the same time it is important that theamplification factor of the receiving amplifier, andthe phase displacement, should be kept constantover the whole frequency range. It is pointed outthat the use of band-pass filters is not satisfactorysince this does not ensure the constancy of the phasedisplacements. It is therefore necessary to useamplifiers which automatically adjust their naturalfrequency to the frequency of the incoming e.m.f.Amplifiers with regenerative feedback satisfy thisrequirement, but their gain does not remain con-stant. A circuit is therefore proposed (Fig. 2) usingcombined negative and positive feedback. Thetheory of the circuit is discussed and results ofexperiments are given. It appears that the varia-tion of the gain of this amplifier is of the order of4-8% for a frequency change of 8%, which is quitepermissible for practical purposes. For an Englishversion see Journ. of Phys. [of USSR], No. 1/2,Vol. 4, 1941, pp. 147-150.

ACOUSTICS AND AUDIO -FREQUENCIES

1704. A NEW DOUBLE -LAYER CONDENSERMICROPHONE FOR THE TRANSMISSION OFSPEECH [to give particularly Good Intelligi-bility (for Railway Platform & SimilarControl Purposes) with Imperviousness to

June, 1942

Shock, Moisture, High Temperatures, etc.].-M. Gosewinkel & H. Bauer. (E.T.Z., ,29th Jan. 1942, Vol. 63, No. 3/4, p. 5o :summary only.)

To obtain the best possible intelligibility themicrophone and its associated equipment is designedto emphasise the higher frequencies, at and oneither side of 4000 c/s : the microphone alone givesgood transmission between about 250 c/s and6000 c/s but its transformer reduces the output ofthe lower frequencies. The large diameter and smallair gap enables the capacitance to the large com-pared with the cable capacitance, so that the pre-amplifier stage need no longer be combined with themicrophone but may be connected by a 200 m cable(cf. Reichardt, 1083 of April). The term " double -layer " is due to the fact that the dielectric is partlyair and partly a solid synthetic material : the soliddielectric is combined with the vibrating diaphragm,by making the moving electrode in the form of ametallic layer deposited on the diaphragm. Betweenthe two electrodes there is an interposing layer withseven circular apertures : this divides the whole intoseven small condenser microphones and gives thediaphragm high natural frequencies without theneed for it to be tightly stretched. The fixedelectrode is provided with holes to allow thepassage of air as the diaphragm vibrates. For anillustrated summary see Alta Frequenza, Feb. 1942,Vol. I I , No. 2, pp. 99-101.1705. THE " VIVAVOX INTERCOMMUNICATION SYS-

TEM.-(Bull. Assoc. suisse des Elec., 19thDec. 1941, Vol. 32, No. 25, pp. 726-728.)

1706. TRANSVERSE VIBRATIONS OF TRIANGULARMEMBRANES.-B. R. Seth. (Sci. Abstracts,Sec. A, Dec. 1941, Vol. 44, No. 528, p. 394.)

1707. A DISCUSSION OF SEVERAL FACTORS CON-TRIBUTING TO GOOD RECORDING.-R. A.Lynn. (Journ. Acous. Soc. Am., Jan. 1942,Vol. 13, No. 3, p. 331 : short summary only.)

1708. DEVELOPMENT LINES OF SOUND -LAMP TECH-. NIQUE [Survey of Patents for Lamps forSound Tracks of Films : Their ParticularRequirements, fulfilled by Special Design orCompensating Circuits].-J. Baltzer. (E.T.Z.,9th Jan. 1941, Vol. 62, No. z, pp. 31-33.)

1709. DISTORTION TESTS BY THE IN TERMODULA-TION METHOD [" for Commercial Testing ofAudio, Radio, & General Sound -RecordingEquipment "] J . K. Hilliard. (Proc. I.R.E.,Dec. 1941, Vol. 29, No. 12, pp. 614-620.)

" As the intermodulation-test is approximatelyfour times as sensitive as the harmonic -analysismethod, it approaches the sensitivity of the ear indetecting intermodulation effects, and it is a, veryvaluable tool with which to measure distortion."1710. A NOTE -FREQUENCY SPECTROMETER AND

NOTE -FREQUENCY SPECTROGRAPH WITH IN-ERTIALESS COMMUTATOR. - P. Vetterlein.(Zeitschr. f. tech. Phys., No. 1, Vol. 23, 1942,pp. 17-24.)

Freystedt's " audio - frequency spectrometer "(1[474 of 1936 [see also 3943 of 1935]) with itscathode -ray -tube indication has become indispens-able for the investigation of speech, but it involves


the use of a motor driving two extremely carefullydesigned and constructed commutators. If onlyfor the elimination of the noise, the substitution ofan electronic arrangement would be a great advan-tage. This has been done in the equipment heredescribed, and has brought with it additionalsimplifications.

The writer describes his search for a satisfactoryelectronic commutator. He refers to the survey ofexisting devices contained in Raabe's paper onmultiplex transmission (859 of 1940), and also toKramolin's suggested arrangement of a c.r. tubewith rotating ray (no reference is given, but forRussian work on such devices see, for instance, 1642& 4255 of 1937 and 4524 of 1940: also cf. 2626of 1938). This latter scheme has its advantages,but is too complicated for a sound analyser. On

1 the other hand the circuit adopted by Raabe issimple in itself but requires a pulse generator which,for a large number of analysing channels, wouldbecome too elaborate and unreliable.

The writer therefore directed his thoughts onthe following lines : the processes of the analyserrequire that a succession of d.c. voltages (i.e. thesound components after passing through their

! respective filters and after rectification and storageIin their respective storage condensers) should be

t- connected in turn ; but, simultaneously, that thecathode ray should be deflected along its time axisin synchronism with this series of switchings. Theobvious thing to do, therefore, is to base the wholeprocess on the time -axis deflection and to devisean arrangement which connects up each channel inturn according to the deflecting voltage obtainingat any particular moment, which measures thevoltage belonging to that channel, and whichmakes it visible. The first realisation of such anarrangement was based on the use of dry -platerectifiers, each channel having its own controlcircuit shown in Fig. 2 ; a three -channel system(Fig. 3) was built but was found to have severaldisadvantages, not the least being that eachchannel required four rectifiers and three trans-formers.

The final solution was found to lie in replacementir of the control circuit of Fig. 2 by a hexode circuitJ in a controllable saturation connection (Fig. 4).Here the electrons emerging from the cathode andaccelerated to the grid G2 pass through this andtraverse at constant speed the field -free spacebetween G, and G3 (which is at the same potentialas G,), and reach the anode A (also at the samepotential) only if the retarding grid G4 is at apotential lying between that of the cathode andthat of the anode : if G4 is more negative than thecathode, the electron velocity will not be greatenough to run counter to the field of G4, and theelectrons will be deflected back to G3 : but if G4

) is even slightly positive to the cathode, all electronsnot actually striking G3 will reach the anode. Thus.while G4 is negative .1. will remain zero, rising

! almost vertically to a definite saturation valuewhen G4 is at zero with respect to the cathode (full-line curves of Fig. 5 : a, b and c show how thevalue of the saturation current depends on thevoltage on the first grid, G1). The lower and upperbends are extremely sharp and the current, outsidethe critical region of G4 potential, extremely con -

27:3

stant. A three -channel commutator made up fromthree such valves is seen in Fig. 6 : all the cathodes,anodes, and G,, G3 grids are interconnected, andthe retarding grids G4 are connected also, but withthe interposition of small potential sources, batteriesor potential -dividers. The varying control voltageU, is applied between the first G4 and the cathodes,and the total anode current from the three valves,as a function of this voltage, takes the " flight ofsteps " form shown in the oscillogram of Fig. 7,the height of the steps being adjustable by thebias on G1. Finally a differentiating circuit (witha nickel -iron -cored inductance) is introduced intothe common anode lead, to give a voltage peak onlywhen the anode current changes as it mounts astep (see dia/d Us curve of Fig. 8). The height ofthese peaks depends (apart from the change of U,with time) only on the bias on the first grid of thevalve concerned. Each d.c. voltage to be switchedon (that is, in the spectrometer, each storage con-denser) is connected to the first grid of the valvebelonging to its channel, and the voltage peaks areamplified, rectified, and applied to the deflectingplates of the c.r. tube. It is from the time -basevoltage of this tube that a fraction is tapped off toprovide the synchronous U3. This 'voltage can besupplied by the mains, which helps to make thewhole apparatus extremely simple compared withthe Freystedt equipment.

Fig. io shows a ten -channel commutator circuitwith its amplifier and c.r. tube. In addition to thelatter, used for visual observation, a double -looposcillograph can be connected to the output : oneloop can record the complete sound curve, whilethe second gives another trace, above this, whichat intervals depending on the commutating speed(1/25th second for 50 c/s mains) reproduces, thecomponent -tone spectrum. The whole equipmentis then known as a note -frequency spectrograph.

1711. PROPAGATION OF SOUND. THROUGH THEATMOSPHERE.-B. Haurwitz. (Journ. Roy.Aeron. Soc., April 1942, Vol. 46, No. 376,pp. 125-126: summary only.)

1712. ON THE THEORY OF CYLINDRICAL ANDSPHERICAL WAVES IN FRICTIONLESS GASESAND LIQUIDS. --H. Marx: (Ann. der Phys.,6th Feb. 1942, Vol. 41, No. 1, pp. 61-88.) Onphysical implications of some of Bechert'sresults (2361 of 1941 and 20 of January.)

1713. THE ACOUSTICAL SOCIETY AND NOISE ABATE-MENT, and BIBLIOGRAPHY ON NOISE.-P. E. Sabine. (Journ. Acous. Soc. Am.,Jan. 1942, Vol. 13, No. 3, pp. 207-209:p. ZIG.)

1714. REPORT OF ACTIVITIES OF THE NATIONALNOISE ABATEMENT COUNCIL, and CITYNOISE.-G. P. Little & F. E. McGee :S. W. Wynne. (Journ. Acous. Soc. Am.,Jan. 1942, Vol. 13, No. 3, pp. 211-213:pp. 214-216.)

1715. HISTORY OF NOISE ABATEMENT IN NEWYORK CITY, and GREATER CHICAGO NOISESURVEY.-E. H. Peabody : H. A. Leedy.(Journ. Acous. Soc. Am., Jan. 1942, Vol. 13,No. 3, p. 332 : p. 332: summaries only.)


1716. THE DESIGN OF THE CELLS OF AN ACOUSTICFILTER WHEN THE DIMENSIONS OF THECELLS ARE NOT SMALL IN COMPARISON WITHTHE WAVELENGTH.-B. K. Shapiro. (Journ.of Tech. Phys. [in Russian], No. 5, Vol. I1,1941, pp. 460-473.)

A theoretical discussion of sound absorption bya series of expansion chambers (cells) connected bypipes, as used with internal combustion engines,ventilators, etc. A cell of dimensions comparablewith the length of the incoming sound wave isconsidered and its constants and sound -absorptioncharacteristic are determined. An experimentalverification of the theory has been made.1717. AN EXPERIMENT ON MIDDLE -EAR DEAFNESS

[leading to Removal of Phase -ReversalDifficulty in Explanation of OtoscleroticDeafness], and THE TEMPORARY DEAFNESSOF BIRDS [Cochlear Response reduced whenMouth is Opened].-K. Lowy : C. W. Bray& W. R. Thurlow. (Journ. Acous. Soc. Am.,Jan. 1942, Vol. 13, No. 3, pp. 335: summaryonly.)

1718. THE PHYSIOLOGY OF THE HUMAN EARTREATED' BY THE METHOD OF RECIPROCALREPRESENTATION.-de Gruyter. (See 1629.)

1719. THE NEW " ADDITIONAL " [Booster] RE-PEATER TYPE V42 OF THE STATE BROAD-CASTING COMPANY [for Use in Each BranchLine from Main Amplifier : Special Require-ments : Great Economy in Size & Material,compared with the Type V22, by NegativeFeedback : Use of Type EFI2 Valve].-J. Peters. (E.N.T., Oct. 1941, Vol. 18,No. so, pp. 222-226.) See also 1691, above.

1720. VIEWPOINTS FOR THE DEVELOPMENT ANDMANUFACTURE OF TELEPHONE LINE AMPLI-FIERS [Intermediate 'and Terminal Repeaters:Requirements for Satisfactory Mass Pro-duction : Statistical Investigation : NewRepeater using Screen -Grid Valves in placeof the Ba Triode : etc.].-M. Kluge. (E.N.T.,Nov. 1941, VOL 18, No. 11, pp. 252-263.)

1721. SENSITIVE FLAMES : III [HydrodynamicProcesses : Flames as Amplifiers of Motion :Electrical Excitation : etc.].-H. Zicken-draht. (Sci. Abstracts, Sec. A, Dec. 1941,Vol. 44, No. 528, p. 394.) For previouswork see 1934 Abstracts, p. 567, r -h column.

1722. THEORETICAL AND EXPERIMENTAL STUDY OFSUPERSONIC GASEOUS JETS.-D. Riabouchin-sky. (Comptes Rendus [Paris], 29th Sept.1941, Vol. 213, No. 13, pp. 424-428.)

1723-. PREPARATION OF QUARTZ ULTRASONIC OSCIL-LATORS [for Use in Investigation of " CertainIrrigation Problems "].-R. R. Bajpai &V. I. Vaidhianathan. (Sci. Abstracts, Sec. A,Dec. 1941, Vol. 44, No. 528, p. 395.)

PHOTOTELEGRAPHY AND TELEVISION1724. TELEVISION-THE SCANNING PROCESS.-P.

Mertz. (Bell Tel. S. Tech. Pub., MonographB-1324, 24 pp.) Dealt with in 1103 of April,where the author's name was spelled wrongly.

June, 1942

1725. AUTOMATIC RADIO RELAY SYSTEMS FORFREQUENCIES ABOVE 500 Megacycles [withParticular Reference to Successful R.C.A.Experimental Transmission of TelevisionSignals through Several Unattended Re-peaters without Demodulation & Remodula-tion : etc.].-J. Ernest Smith. (Proc I.R.E.Dec. 1941, Vol. 29, No. 12, p. 666: summaryonly.)

1726. A SIMPLE TELEVISION DEMONSTRATION SYS-TEM [150 -Line Equipment using the SmallIconoscope : Total Cost less than That ofCommercial -Type Iconoscope alone].-J. B.Sherman. (Proc. I.R.E., Jan. 1942, Vol. 3o,No. 1, pp. 8-15.) For this small iconoscopesee 3090 of 1940.

1727. ORTHICON PORTABLE TELEVISION EQUIP-MENT [particularly for Adverse Light Con-ditions : Novel Features, including. ForcedAir Cooling of Power Transformer andRegulator & Rectifier Valves].-M. A.Trainer. (Proc. I.R.E., Jan. 1942, Vol. 30,No. s, pp. 15-19.) A summary was referredto in 1108 of April.

1728. MOBILE TELEVISION EQUIPMENT [CameraEquipment for Studio & Outdoor Use :Mobile Camera -Control Dolly, ElectronicView -Finding System, Synchronising Equip-ment, etc.].-R. L. Campbell & others.(Proc. I.R.E., Jan. 1942, Vol. 3o, No. ,,pp. 1-7.) From the DuMont Laboratories.

1729. MOTION -PICTURE LENS WITH VIBRATEDAUXILIARY LENS MAINTAINING " UNIFORMSOFT FOCUS" FROM FOUR FEET TO IN-FINITY.-(Sci. News Letter, 28th Feb. 1942,Vol. 41, No. 9, p. 143: paragraph only.)Cf. 2758 of 1941.

1730. AMPLIFICATION BY SECONDARY -ELECTRONEMISSION IN STATIC MULTIPLIERS.-Schrdt-ger. (See 1692.)

1731. FACTORS GOVERNING PERFORMANCE OF ELEC-TRON GUNS IN TELEVISION CATHODE-RAYTUBES [Derivation of Formula for UpperLimit of Useful Beam Current].-R. R. Law.(Proc. I.R.E., Feb. 1942, Vol. 3o, No. 2,pp. 103-105.)

" For any given structure, the ratio of themeasured beam current /to the computed limitingvalue affords a figure of merit describing the per-formance of the gun. This ratio is ordinarily aboutone -tenth (Jacob, 3625 of 1939), but by minimisingthe effects of space charge in the first -crossover -forming region, Pierce (4275 of 1940) has obtainedcurrent densities of over one half the limitingvalue."

1732. IMAGE ERRORS OCCURRING IN THE DE -ELECTION OF A CATHODE-RAY BEAM IN TWOCROSSED DEFLECTING FIELDS.-G. Wendt.(ZeitSchr. f. Phys., 1st Feb. 1942, Vol. 118,No. 9/1o, pp. 593-617.)

From the Telefunken television laboratories.The deflection equations and deflection errors fora single deflecting organ with double symmetryi.e. having two planes of symmetry at right angles


to each other and passing through the tube axis)are already known : references are given to Glaser,1577 of 1939, and to the present writer, 3225 of1939. In c.r. oscillographs, however, and in tele-vision pick-up cameras and receivers, and c.r.commutators, two fields are always employed,deflecting in directions at right angles to each other.There occur then, in addition to the deflectionerrors characteristic of each field, further errorsdue to the interaction of the two, fields. Theseare not, 4undamentally, of a new type, but theymust be taken into account if an error -free tele-vision raster or cathode-ray oscillogram is to beobtained. " For this reason the deflection lawswill be derived in the following pages for a systemcomposed of two mutually perpendicular deflectingfields, and the error -coefficients calculated. Finally,the form of the error for a central beam (i.e. oneincident in the direction of the axis of the system)will be discussed in detail. It is usually possiblein special applications to replace the more or lesscomplicated expressions for the error -coefficientsby simplified and clearer formulae. For the ex-ample of a system composed of two similar magneticdeflecting fields w th coincident principal planes,such simplifications are given, and with theirassistance an investigation is carried out on theavoidability of the errors." The two deflectingsystems are assumed to be either both purelyelectrostatic or both purely magnetic : " the useof a combined field is generally rejected on accountof the elaborateness of the circuits." The inde-pendent and just published work of Picht & Himpan(3o91 of 1941) is referred to in a footnote : it deals

rl with the deflection errors of electrostatic fieldsonly, deflecting in two directions and extendingindefinitely in one direction, and the treatmentof the series development and of the error calcula-tion represents a different viewpoint.

It is shown that the errors occurring are (i)distortion (Fig. 4 : deformation of the whole image,not of the spot : independent of the ray crosssection, and taking the form of " scale distortion,"diagrams b -e : of coordinate curvature, either of" pincushion " or " barrel " type, diagrams f -k :or more generally a combination of scale and co -

1 ordinate distortions, diagrams 1 & m) : (ii) astig-matism, isotropic and anisotropic (increasing linearlywith the ray radius at the deflecting field)

: and(iii) coma, increasing as the square of the rayradius. These last two types of error affect theform of the spot only, not that of the raster orimage. The investigation, mentioned above, ofthe possibility of eliminating these errors in aspecial case is carried out on pp. 613-617. Coma

0 is the only type that can be eliminated completely;

for the others a compromise must be arrived at.

1733. THE MOST FAVOURABLE FORM OF SO-CALLED" MAT " COILS FOR MAGNETIC DEFLECTIONIN CATHODE-RAY TUBES. - H. Scholz.(E.N.T., Nov. 1941, Vol. 18, No. ii, pp.239-246.)

The design of deflecting coils involves twoproblems, the determination of the number ofturns, based on the current available from theexternal circuit, and the obtaining of a homo-geneous magnetic field so that image distortion

275

may be avoided. " On the first problem severalpapers have already appeared [Bahring, 3628 of1939: Gunther. 219 of 1940 : Philips MinitualtMouatshefte, 1939, Nos. 66 & 73], while on thelatter only a single paper exists [the Philips journal.No. 69, 1939, is again cited], which by testingvarious forms of ' mat ' windings and obtainingthe lines of force by means of iron filings seeks toobtain the best, most uniform field." Many formsof coil exist (for type names a paper in Telefunken-l?ohre, March 1941, No. I9/20, is referred to) butthey all have one point in common : they arewound as " concentratedly " as possible, each newwinding being arranged as like as possible to thelast, so that the resulting coil can be treatedtheoretically as a single conductor of the appro-priate shape.

The present paper deals with a type of windingin which the individual turns are not " concen-trated " but deliberately wound side by side as ina door -mat, the " mat " being curved so as to fitround part of the tube neck. The object of thepaper is to determine how much of the neck shouldbe left uncovered by a pair of " mats " in orderthat the field may be most homogeneous. It isconcluded that the best design of deflecting coilis a pair of " mats " having an internal apertureangle of 2 x 28.5 = 57 : that is, two uncoveredarcs of neck are left, each subtending 57' at theaxis of the tube.

1734. THE DISPLACEMENT, IN TIME, OF SERIES OFPULSES [Synchronising Signals, for theCorrect Mixing of Pick -Ups at VariousDistances from the Transmitter]. - K.Briickersteinkuhl. (E.T.Z., 12th Feb. 1942,Vol. 63, No. 5 6. pp. 75-76 : summary, from

Fernseh-A .G., Vol. 2, 1941, p. 46onwards.)

The synchronising signals sent out from thecentral station reach the various pick-up pointswith different delays, and the image signals sentback to the central station also suffer delays de-pending on the length of the cable. The transittime in a television cable about 25 km long amountsto 90.7 ps, corresponding to the time for tracingone line of a 44i -line image : this is taken as thestandard. Since no image signals, but only thesynchronising signals, have to be delayed in orderto carry out the equalisation, the necessary circuitsare comparatively simple, but if these signals hadto be transmitted with fidelity of form abouti000 choke sections would be required, whichwould mean considerable attenuation from eddy -current losses in the windings and iron cores.Luckily such fidelity is not necessary, and a90.7 p_s delay can he obtained with only 100 sec-tions : the distorted signal emerging from thenetwork is reconverted into rectangular form byan amplifier. The arrangement is seen in Fig. 4.

1735. A METHOD OF LIGHT MODULATION BASEDON THE USE OF A QUARTZ CRYSTAL AT HIGHVOLTAGES.-Mandelstam & others. (Men-tioned in 1755, below.)

1736. THEORETICAL CONSIDERATIONS ON A NEWMETHOD OF LARGE -SCREEN TELEVISIONPROJECTION : PART II. -F. Fischer & H.


Thiemann. (Schweizer Arch. f. angew.Wiss. u. Tech., Nov. & Dec. 1941, Vol. 7,Nos. II & 12, pp. 305-318 & 337-344 : tobe contd : in German.)

For Part I see 3080 of 1941. The light -controllingmedium is now given the name " Eidophor "(picture carrier) and the whole apparatus is termeda " Teleidoscope." The November instalmentcontains the following sections :-Introductionand remarks on the general behaviour of the liquideidophor of great thickness : the general theoryof the eidophor of finite thickness (including thecalculation of the electric fields in the interior ofthe eidophor and outside it, the electric forces atthe surface, the elastic displacements and internalstrains, etc.) : picture synthesis and the calculationof the necessary cathode-ray current : etc.

The December instalment extends the theory toa solid eidophor. Here the characteristic equationis a cubic one, in contrast to the quadratic equationof the liquid eidophor :, it is much more difficultto deal with and its treatment is therefore differentfrom the previous one, but otherwise the courseof the investigation is the same. The liquid andsolid eidophors are merely two special cases of thegeneral problem : the nature of an eidophor isdetermined by a quantity y = ocA0/(2G mho),and this is unity for the liquid type where theelastic stresses disappear and surface tension pre-dominates, and zero for the solid type where thesurface tension is negligible compared with theelastic stresses. The type of solid material en-visaged is apparently a kind of jelly consisting ofa cellular -lattice filled with liquid : to simplify themathematical treatment it is assumed to be incom-pressible, like caoutchouc. As before, the treatmentis purely theoretical and no practical points arementioned. The next instalment will comparethe picture quality obtainable with the liquid andsolid eidophors.

1737. IRREGULARITIES IN THE FUNCTIONING OFCERTAIN VACUUM PHOTOCELLS [Caesium -Silver Types, Central Anode Design, byVarious Manufacturers]. - D. Cavassilas.(Comptes Rendus [Paris], 8th Sept. 1941,Vol. 213, No. ro, pp. 346-348.)

Certain specimens displayed marked abnor-malities which disappeared, or were greatly reduced,on applying a magnetic field roughly in the cathode/anode line. These are . no doubt attributable,wholly or partly, to the accumulation of negativecharges on the inner wall (cells with independentcathode plate) or on the window of the bulb (Philips3511, spherical container). " It would be inter-esting to examine the influence of such charges onthe trajectories of the photoelectrons, and toattempt to explain thus the principal phenomenaobserved (discontinuity of current and spectraleffect on the ratio cc)."

1738. THE SPECTRAL SENSITIVITY OF ANTIMONY -CAESIUM PHOTOCELLS.-M. L. Kats [Katz]& R. E. Solomonyuk. (Journ. of Tech.Phys. [in Russian], No. 5, Vol. II, 1941,pp 483-484.)

In view of the discrepancy in the spectral sensi-tivity of antimony -caesium photocells as measured

June, 1942

by various authors, the effect on this characteristicof the value of the voltage applied to the photocellwas investigated. Voltages from 45 to 1035 vwere used and it was found that th general shape ofthe curve and the position of the maximum re-mained unaltered.

1739. A SELENIUM PHOTOCELL FOR LIGHT MEASURE-MENTS.-E. Putseyko. (Journ. of Tech.Phys. [in Russian], No. 5, Vol. II, 1941,

PP 485-488.)In order to make the spectral sensitivity of a

selenium photocell similar to that of the eye eachcell has to be corrected separately by special lightfilters. In the present paper manufacturingmethods are proposed for producing seleniumphotocells with appreciably identical spectralcharacteristics, enabling a standard light filter tobe used.

1740. A STUDY OF ALLOTROPES OF SELENIUM BYTHE X-RAY DIFFRACTION METHOD.-K. D.Gupta & B. B. Ray. (Indian Journ. ofPhys., Oct. 1941, Vol. 15, Part 5, pp. 389-399 )

1741. THE PHOTOCONDUCTIVITY OF NaCl CRYSTALS

IN STRONG ELECTRIC FIELDS. -A. N.Arsen'eva-Geyl. (Journ. of Tech. Phys.[in Russian], No. 6, Vol. II, 1941, pp. 550-554-)

Measurements were made of the photocurrentin NaCl crystals placed in electric fields of gradientsup to 7 x Ios v/cm. A rapid increase of thephotocurrent with the intensity of the field wasobserved. A theoretical interpretation of thisphenomenon is given.

MEASUREMENTS AND STANDARDS

1742. THE ARMED FORCES AND STANDARDISATION[DIN Standards & the HgN (Army), LgN(Aircraft)-, MWaN (Marine), & KM (Navy)Standards].-M. Klein. (Zeitschr. V.D.I.,7th March 1942, Vol. 86, No. 9/10, pp.

129-134.)

1743. GENERAL AMPLITUDE RELATIONS FOR TRANS-MISSION LINES WITH UNRESTRICTED LINEPARAMETERS, TERMINAL IMPEDANCES, ANDDRIVING POINT.-R. King. (Proc. I.R.E.,Dec. 1941, Vol. 29, No. 12, pp. 640-648.)

" The extreme generality and surprising sim-

plicity of the expressions . . . should make thesevaluable in all transmission -line problems for whichless exact formulas are inadequate. These include,in particular, many transmission -line methods formaking electrical measurements at ultra -highfrequencies."

1744. DIRECT -READING WATTMETERS FOR USE ATRADIO FREQUENCIES [Practical Instruments,the First for 500-2000 kc/s, the Second aSingle -Frequency Device for Region near5o Mc/s].-G. H. Brown & others. (Proc.I.R.E., Dec. 1941, Vol. 29, No. 12, p. 664:summary only.)

ti

June, 1942 WIRELESS 277ENGINEER

1745. THE MEASUREMENT OF SMALL POWERS WITHTHE BOLOMETER-BRIDGE.-R. Wallauschek.(E.N.T., Nov. 1941, Vol. 18, No. 11, pp. 247-251.)

From the Telefunken laboratories. The methoddealt with is one in which the resistance changes inthe bolometer wire are measured with a bridge bythe deflection method, as opposed to the nullmethod. The corrections in general necessary arecalculated : for a suitable procedure these are sosmall, when the power to be measured is sufficientlysmall, that a direct reading is correct within a firstapproximation. The bolometer should be workedon the linear part of its characteristic, both becausecalculation is then simplest and because the bolo -meter is then at its most sensitive.

A suitable bridge for the purpose is described :of the remaining three resistances only one need beof the highest precision, since the errors of theother two, and their mutual deviation, do not, inthe first approximation, come into the measurement:it is not necessary, therefore, to balance the re-sistances of the leads. Two methods are given forcalibrating the current in the diagonal against theresistance changes in the bolometer : a generalmethod, in which the reactions of the altered currentrelations on the bolometer are allowed for by acorrecting factor, and the second method, for smallpowers, referred to above. It is mentioned thata further advantage of working on the linearportion of the characteristic, for " a special applica-tion of the bolometer," will be dealt with in afurther paper.

'1746.

1747.

1748.

THE MEASUREMENT OF SMALL CURRENTS ANDVOLTAGES, AND SMALL CHANGES IN LENGTH,WITH THE BOLOMETRIC COMPENSATOR [Freefrom the Dependence on Voltage & Tempera-ture Fluctuations shown by Previous Bolo -meter Arrangements].-L. Merz & H. Niepel.(Wiss. VerOff. a. d. Siemens-Werken, No. 2,Vol. 18, 1939, pp. 28-40.) A summary wasdealt with in 2599 of 1941.A WIDE -RANGE, LINEAR, UNAMBIGUOUS,DIRECT -READING PHASEMETER [using aTime Ratio as a Parameter and deliveringa Direct Current proportional to PhaseAngle : Wide Ranges of Frequencies &Voltages : readily adapted to operation ofRecorders, Servo Mechanisms, etc.].-J. E.Shepherd. (Proc. I.R.E., Dec. 1941, Vol. 29,No. 12, p. 666: summary only.)

A NEW CAPACITANCE AND LOSS -FACTORBRIDGE FOR LOW FREQUENCIES, WITH HANDAND AUTOMATIC BALANCING [Combinationof Schering Bridge and Complex Compensa-tor, for Mains Frequencies : Theory &Construction : Capacitances from a FewPicofarads to some Hundreds of Micro-farads].-H. Poleck. (Wiss. Veroff. a. d.Siemens-Werken, No. 2, Vol 18, 1939,PP 9-27.)

1749. A DIRECT -READING IMPEDANCE COMPARATORFOR PRODUCTION TESTING OF RECEIVERCOILS [R.F. Bridge : Percentage Deviationin Inductance from Pre -Set ReferenceStandard read on Calibrated Scale on which

Tolerance Limits may be marked].-F. M.Leyden & W. R. Baker. (A.W.A. Tech.Review, Dec. 1941, Vol. 5, No. 6, pp. 275-285.)

1750. STANDARD TESTS ON BROADCAST RECEIVERS[based on R.M.A. 1936 Standards & I.R.E.1938 Standards].-V. V. L. Rao. (Electro-technics [Bangalore], Nov. 1941, No. 14,

PP. 40-49.)1751. ON THE MEASUREMENT OF HIGH -FREQUENCY

INTERFERENCE.-Conrad. (See 1659.)

1752. DISTORTION TESTS BY THE INTERMODULATIONMETHOD [" for Commercial Testing of Audio,Radio, & General Sound -Recording Equip-ment "].-Hilliard. (See 1709.)

1753. A NEW TYPE OF APPARATUS FOR THERECORDING OF FREQUENCY CURVES [Of

Amplifiers, Filters, etc., with Pass Bandsbetween o.i and 21 MC/S].-E. Legler.(E.T.Z., 29th Jan. 1942, Vol. 63, No. 3/4,pp. 47-48 : summary, from Mitteil. Fernseh-A .G., Vol. 2, 1941, p. 5o onwards.)

A c.r. tube is used, with a 18 X I I cm2 screen :the frequency axis is linear and not logarithmic,so that a frequency of ioo kc/s corresponds to a2 mm length. The chief point of difference com-pared with previous arrangements is that thevariation of the test frequency is rigidly connectedwith the frequency scale of the indicating tube :this is accomplished as follows.

The signal generator MG sweeps over the range36-44 Mc/s linearly with the exciting current of thed.c.-polarised choke forming the inductance ofits oscillatory circuit : this current is of saw -toothform and is derived from a relaxation oscillator KG,of frequency 25 c/s : it passes also through thedeflecting coil of the c.r. tube, this coil and thechoke polarising coil being in series : in this waythe rigid coupling between the tube scale and thefrequency is attained. To obtain the three fre-quency ranges 0.1-8, 6-14, and 13-21 Mc/s, oneof three auxiliary oscillators, of frequencies 44, 5o,and 57 Mc/s, can be switched onto the mixingstage M. The resulting i.f. oscillation is passedthrough the first stages of a wide -band amplifier :in the output circuit, any one of four resonantcircuits (1, 7, 14, and 21 Mc/s) can be interposedfor the checking, and occasional correction, of thetest frequency against the screen scale. On thefar side of these circuits is the final stage E of thei.f. amplifier : at the output of this the test voltageis checked by a valve voltmeter and maintained ata constant value : a potentiometer Sp allows theoutput voltage to be varied between Too tiv and I v,for introduction to the amplifier or filter undertest, V, and for subsequent amplification (afterrectification if necessary) and application to thec.r. tube. A reversing stage U can be switched into correct the polarity of any rectifier in theamplifier under test.

1754. ON THE TEMPERATURE COEFFICIENT OF THEEQUIVALENT -CIRCUIT CONSTANTS IN QUARTZCRYSTAL VIBRATORS FOR ELECTRICAL WAVE-FILTERS.-Kamayachi & Ishikawa. (See1631.)

278

1755.

WIRELESSENGINEER

THE RELATIONSHIP BETWEEN THE VOLTAGESAPPLIED TO A QUARTZ CRYSTAL AND THELIGHT INTENSITY DISTRIBUTION IN THEDIFFRACTION SPECTRA CAUSED BY THESUPERSONIC WAVES SO PRODUCED [Voltagesup to 15oo Volts].-K. N. Pogodaev. (Journ.of Tech. Phys. [in Russian], No. 5, Vol.1941, PP 474-478.)

Experiments are conducted in connection witha new method for light modulation proposed byMandelstam, Papalexi, & Landsberg. The methodis based on the relationship between the intensityof the diffraction spectrum and the intensity ofsupersonic oscillations (or voltages applied to thecrystal). In these experiments diffraction spectrafrom zero to the seventh order inclusive werestudied, and voltages applied to the crystal variedfrom o to 1500 v.

1756. A QUARTZ PLATE WITH COUPLED LIQUIDCOLUMN AS A VARIABLE RESONATOR [Theory& Experiment].-F. E. Fox & G. D. Rock.(Proc. I.R.E., Jan. 1942, VOL 30, No. t,PP. 29-33.)

The resonance (or oscillation) frequency of acombination consisting of a quartz plate and acoupled water column was varied over a widerange (2.2-3.o Mc/s) by properly tuning the liquidcolumn, and the sharpness of resonance of such aresonator was increased to some ten times that ofan unloaded quartz plate similarly mounted on asupport (the plate was cemented to a brass discover an opening slightly smaller than the plate)." There is no doubt that by the use of a liquid suchas mercury instead of water the sharpness ofresonance oould increased, and that thiswould permit an even greater shift in the resonantfrequency."1757. LONGITUDINAL VIBRATIONS OF SQUARE

QUARTZ PLATES.-R. Bechmann. (Zeitschr.f. Phys., 1st Feb. 1942, Vol. 118, No. 9/1o,PP. 515-538.)

From the Telefunken laboratories. " Systematicinvestigations of the longitudinal vibrations ofsquare plates of crystalline material, especiallyquartz, oriented arbitrarily with respect to thecrystal axes, have hitherto not been available ",though papers dealing with special cases are citedand reviewed briefly, ranging from Voigt's 1928differential equation to Builder & Benson's paperdealt with in 3440 of 1941: " In a general in-vestigation carried out by the writer on the elasticnatural frequencies of an anisotropic body ofparallelepiped form (2183 of 1941) there is to befound also, as a limiting case [infinitely thin plate],a solution for the longitudinal vibrations of crystal-line plates of arbitrary orientation. For a rect-angular plate this solution yields three differentlongitudinal vibrations. In the following paper therange of validity of this solution will be investigatedby measurements on numerous differently -orientedquartz plates ".

From the author's summary :-" The naturalfrequencies are roots of a third -order equationrepresenting the interaction of three degrees offreedom, two longitudinal and one transverse. Theagreement between calculated and measured naturalfrequencies of the purely longitudinal vibrations is

June, 1942

very good. For the transverse degree of freedomthe frequency equation requires a correcting factorwhich is determined empirically [constant a: seefor example eqns. 7b and 8b : its value variesslightly with 8, an average being 0.877], in order toobtain satisfactory agreement between the cal-culated and measured natural frequencies of thefundamental oscillations of square plates of variousorientations. In addition to the three naturalfrequencies given by the calculations, there some-times occurs a fourth frequency [also of the char-acter of a longitudinal vibration (curve N4 ofFig. 9, and bottom of pp. 535 & 537) : " origin atpresent unknown "]. The transformations of theelasticity coefficients and the piezoelectric coeffi-cients for arbitrary orientations of the plates,which give the electrical excitation possibilities ofthe natural frequencies, are carried out by meansof the Euler angles for right -rotating and left -rotating quartz crystals ". It has been mentionedthat the calculations are based on the assumptionof infinitely thin plates : in the experimental platesthe ratio of side length to thickness was about17 : I. This can be considered as sufficient, for acheck experiment with the side length kept con-stant and the thickness reduced to 0.5 mm gavea change of less than o.5%p in the vibration co-efficient. The writer ends by mentioning twopoints which require clearing up before the processesof the longitudinal vibrations of square and rect-angular plates can be considered as finally settled.

1758. VARIABLE - FREQUENCY BRIDGE - STABILISEDOSCILLATORS [incorporating Thermal Devicefor Amplitude Control].-W. G. Shepherd &R. 0. Wise. (Proc. I.R.E., Dec. 1941,Vol. 29, No. 12, p. 666: summary only.)

1759. PERMEABILITY, INDUCTANCE, AND HYSTE-RESIS RESISTANCE FOR SINUSOIDAL FIELDSTRENGTH AND FOR SINUSOIDAL INDUCTION.-G. Macke. (E.N.T., June 1941, Vol. 18,No. 6, pp. 121-125.)

Following Rayleigh's example, later investigatorshave assumed a sinusoidal field strength, involvinga distortion of the magnetic induction as a resultof hysteresis-the induction contains, in additionto the fundamental, all the odd harmonics. Inpractical measuring technique, however, it happensthat sinusoidal voltages, not currents, are employed :this means that the induction, not the field strength,is sinusoidal. The writer therefore investigateswhether the expressions for permeability, induct-ance, and hysteresis resistance, originally obtainedfor sinusoidal field strengths, are still valid forsinusoidal induction : he finds that the formulaefor the second case are different, but that for thesmall magnetic forces usual in communicationengineering the discrepancies are negligible inpractice, being only a small percentage.

1760. THE MAGNETIC INDUCTION FIELD OF AIR -CORE COILS AND ITS APPLICATION TO HIGH -FREQUENCY HEATING IN VALVE MANU-FACTURE.-Kirkpatrick. (See 1695.)

1761. A MAGNETOMETER WITH ASTATIC SYSTEM INA HOMOGENEOUS COIL FIELD [particularlysuitable for Measurement of Low Coercive

Li

June, 1942

1762.

WIRELESSENGINEER

Forces in Small Samples].-H. Neumann.(Wiss. Veraff. a. d. Siemens-Werken, No. 2,Vol. 18, 1939, pp. 41-44)AN ABSOLUTE DETERMINATION OF THEAMPERE, USING HELICAL AND SPIRAL COILS[including Sections on Computation ofForces between Coaxial Helices and betweenHelix & Spiral].-R. W. Curtis & others.(Journ. of Res. of Nat. Bur. of Stds., Feb.1942, Vol. 28, No. 2, pp. 133-157.)

SUBSIDIARY APPARATUS AND MATERIALS

I 763 . A NEW PRINCIPLE FOR STABLE D.C. AMPLI-FICATION [for Process Control & OtherPurposes] .-Eberhardt & others. (See 1633.)

1764. AN INERTIALESS COMMUTATOR [primarily fora Note -Frequency Spectrometer] USINGHEXODE VALVES IN A CONTROLLED -SATURA-TION CONNECTION .-Vetterlein. (In paperdealt with in 171o, above.)

1765. IMAGE ERRORS OCCURRING IN THE DEFLEC-TION OF A CATHODE-RAY BEAM IN TwoCROSSED DEFLECTING FIELDS . -Wendt. (See1732.)

1766. ON THE, MOTION OF AN ELECTRIC PARTICLE.--Opatowski. (See i6or.)

1767. TRAJECTORIES OF MONOENERGET IC ELEC-TRONS, IN AN ARBITRARY STATIC ELECTRO-MAGNETIC FIELD, IN THE NEIGHBOURHOODOF A GIVEN TRA J ECTORY.-MacColl. (Journ.of Math. & Phys. [of M. I . T.] , Dec. 1941,Vol. 20, No. 4, pp. 355-369.)

From the Bell Telephone Laboratories. " Muchof the existing theory of electron optics is concernedwith the study of the trajectories in the neighbour-hood of the axis of a static axially symmetricelectromagnetic field. In the present paper thistheory is generalised in that we consider electronsmoving with fixed total energy E in an arbitrarystatic electromagnetic field, and we study the tra-jectories in the neighbourhood of an arbitrarytrajectory To. Specifically, we investigate thevarious types of images which can be formed, theconditions for their formation, the various types ofdistortion to which the images are subject, etc.This general problem seems to have been discussedon only one previous occasion (Cotte, 2921 of 1939and back reference [also 663 of 1938]), and thenwith but little overlapping of the discussion givenhere. We confine our attention to ' first ordereffects,' in the sense that certain distances, whichcharacterise the departures of the trajectories underconsideration from the basic trajectory To, areassumed to be so small that their squares andproducts can be neglected . . ."

1768. THE EFFECT OF SPACE CHARGE ON THEPOTENTIAL AND ELECTRON PATHS OF ELEC-TRON BEAMS.-Petrie. (See 1684.)

1769. THE MOST FAVOURABLE FORM OF THE SO-CALLED " MAT " COILS FOR MAGNETICDEFLECTION IN CATHODE-RAY TUBES . -Scholz . (See 1733.)

279

1770. FACTORS GOVERNING PERFORMANCE OF ELEC-TRON GUNS IN TELEVISION CATHODE-RAYTUBES.-Law. (See 1731.)

1771. THEORETICAL AND EXPERIMENTAL RE-SEARCHES ON ELECTRON RADIATORS [pri-marily in connection with X -Ray Tubes].-Dosse. (E.T.Z., 16th Jan. 1941, Vol. 6z,No. 3, pp. 57-58 : summary, from Zeitschr.f. Phys., Vol. 115, 1940, p. 53o onwards.)

On the basis of the Maxwellian velocity -distribu-tion, Law has calculated the current density atthe focus as a function of the distance of the pointof measurement from the axis : his equationinvolves the total current, the accelerating voltage,and an unknown constant a. The writer finds avalue for a in terms of the true cathode temperatureand the focal length, and from this he derives otherrelations important in regard to the merit of anarrangement. The theoretical results are satis-factorily confirmed by tests with the special ray -measuring device of Fig. 3, except that a definiterelation between focal -spot size and cathodetemperature has not so far been established.1772. THE APPLICATION OF THE CATHODE-RAY

OSCILLOGRAPH TO THE MEASUREMENT OFTHE INCLINATION VECTOR. - Goncharski.(Journ. of Tech. Phys. [in Russian], No. 5,Vol. II, 1941, pp. 479-482.)

A method is proposed in which the inclination ofa system, for example of a pendulum, can bedetermined at a remote point by observing a vectoron the screen of an oscillograph. . The magnitudeand direction of this vector indicate respectivelythe degree and sense of the inclination of thesystem. In the example considered (Fig. 1) acoil 2 is attached to the suspension of the pendulum.Round this coil four other coils 3 are mounted andfed with two- or three-phase current. A rotatingmagnetic field is thus produced, but an e.m.f. isinduced in coil z only if the pendulum, and thereforethe coil, are inclined. The e.m.f. so generated istransmitted to the plates of the oscillograph. Atthe same time one of the voltage phases feedingcoils 3 is transformed into short impulses whosephase depends on the direction of the inclination ofthe pendulum. The impulses are transmitted tothe modulating electrode of the oscillograph anda dark radial line is obtained on the luminous circleon the oscillograph screen. The theory and accuracyof the method are discussed in detail and a modifi-cation of the method proposed is also considered.1773. INCREASING THE RESOLVING POWER OF THE

EMISSION -TYPE ELECTRON MICROSCOPE .-Boersch. (Naturwiss., loth Feb. 1942,Vol. 3o, No. 8, p. 120.)

Bruche & Knecht (853 of 1935) gave the re-solving power of such a microscope as 3µ, and sincethen nothing has been heard of an experimentalraising of this value. Since the problem is im-portant for the metallographic, thermionic, andphotoelectric research on surfaces, the writer hastried to accomplish this. A directly heated molyb-denum ribbon was magnified with a purelyelectrostatic immersion objective of the Briiche-J ohannson type (Johannson, 1934 Abstracts,p. 51). In order to use higher voltages (3o kvinstead of the previous 2 kv) and higher field

MIKLIENGENELK

strength, i 5o kv cm instead ' kVtween Wefinelt cylinder and anode the systeinhad to be- iniditied the basis 1.1t previous ex-perience in the development of high -voltage lenses!the reference given is meaningless. but se,- 1571 of194, : further. the syStem of internal photo-graphy was adapted to electrein-miereiscopy,that the coarse grain ief the fluorescent screen wasreplaced by the tine grain of the photographicfilm As a result of these changes the resolutionwas increased from 3,e/ to 0ce7ja itig. 31. which isbetter than the o.2,gi of the optical microseeipe andeven than the theoretical limit for the emissionmicroscope- given by Recknagel as o.13µ for thesame conditions (held strength at cathode3o kv cin 1 51.4 of February). Moreover, theexperimental construction of the objective couldbe improved as regards axiality, and this and otherimprovements would no doubt raise the resolvingpower still further : another step forward wouldbe the use of indirect heating, to eliminate themagnetic Held due to the current along the molyb-denum foil. Since the aperture error is an im-portant factor in limiting the resolving power,precautions taken in the transmission -type micro-scope to reduce this error (see Boersch's " TheProblem of Image Formation," Ph Bf-richte,1st Dec. 1940, Vol. 21, No. 23, p. 2300). such asthe introduction of stops, would effect a furtherimprovement in the present case : in this connectionthe writer's experiments with very small stopsmade of ocer5 min platinum foil and introducedat the anode (1174 of 1941) showed that these wouldstand up to the heat resulting front electron bom-bardment if they were protected by larger stopsin front of them.

In the actual experimental model the immersionobjective (Fig. 1) had a focal length of 3.o9 mm :the distance between the Wehnelt cylinder (1.3 mindiameter) and the amide was 2 mm.1774. FURTHER DEVELOPMENTAL WORK ON THE

UNIVERSAL ELECTRON MICROSCoEE leadingto Latest Type with Alternative- Magnetic(o.9 mm) or Electrostatic Objective, forBright -Field or Dark -Field Working, Stereo-scopic Working : with Object Shading (forProtection of Sensitive Objects), Object Re-action Chamber, Object Heating : VacuumFilm Camera : Electron Diffraction Working :etc.'. --von Ardennes (Ph ysik. Zeit.schr., Jan.1942, Vol. 43, Ni.,. 1 2, pp. I i--15.) This is thepaper referred to in r 250 of April. Seealso 1775, below, and 3595 of 1041.

1775. HEATING-SUPERMICROSCOPY WITH THE N

VERSAL ELECTRON MICROScoPE. vonArdenne. Zeitschr., No. 3, Vol, 07,1941, p. 257 onwards.) Referred to in thepaper dealt with in 1774. above, where thespecial importance of the provision ofobject -heating for electron-dittraction workis emphasised.

177o THE ExTENSION OF THE RANGE OF WORKINGof MAGNETic VOLTAGE STABILISERS --Beck.

12th Feb. 11)42, Vol. 03, No. 5 0,pp. 57o0.)

From the Siemens c't: Halske laboratories. Thewell -know -n stabiliser consisting of an unsaturated

I1111 11,112

ice srres Clk-111 ilt and a satur.ttcd Lokecombination as 1146 -

hitherto I \AI used to Ted LICt. Mani,up ti 1tug TO a value am 01.111d h a con-stant load the all

5 or less. These stabilise , has c beenemployed on mains systems 01 dittei, lit 5 oltage,.but such a use has meant a good, deal ot c hanging -(0, er and parallel chokesk 11.1 I, lug

time it has been desired to obtain a v,ktage stabiliserwhich could be used w dhout c han2e OA all tinecustomary mains vintagesin Germans I hi, wandmean an extension of the range \ a

variation e)1 middle \ v

A thorough investigation the V t. I, ,IA,I',.!1111$

under various conditions, of the i1 iii iI cite liltled to the conclusion that what was leilun,d wasa full utilisation of the saturation thole, gist anextended range, and a recluetion in the \ thyseries choke, to give rtiiricncv Instead i,r thefundamental circuit of Fig Ia. the " 55 ide-rangestabiliser circuit of Fig. rc was adopted. theInductance of the series choke bring k'd

about half the usual value. This recit, thin in-creased the danger ut excitationic la x anonoscillations, -well known to occur ill V I', ,1141.1t

circuits consisting of a eondenser and a saturatedchoke ):,/-e. for example. Aretz. 21 i,i ut ii g butthis defect was eliminated by the intiodmuiiiin series with the condenser. of a -001,i1,1cgapped choke to de -tune the CID.. tilt <u i 2,11 is thesecond harmonic which is found to be :lustof the trouble this elnike is included ui I le 1,

The stabiliser thus obtained has a ei oily 111;4 Fang(' of90-250 v and gives a 2

control. It designed for special acturary alid with-out troubling too much about efficiency and c. ,irony,the output voltage can be kept within

1777. (Pt THE 'ARAM!, I ENS OF AN 1511'1 Itit,',R A TOR OPERATING \\Atli A I)ISi. HA Rut- I

)rsunsii . (./ ou . I cch.Russian No_ o, Vol. r i, 1941. pp. 501-575.)

It is pointed out that discharge operatingat voltages of the ()flier of a megavolt impose specialrequirements on the associated impulse generator.An equivalent circuit of the system ihig i i is givenand the of operation is d 1,..1.1:,,,C1.1 In detailFormulae are derived for determining the generatorvoltage and the current flossing in the gene -Futoncircuit before and during the discharge A numberof calculated and experimental cures arc shownand the effects of various parameters of the generatoron the spectrum of the particles generated by thetube are considered. The niatn cone lusion reachedis that contrary to the usual practice an impulsegenerator to operate with a discharge tube shouldpossess large self-inductance, large parasitic capa-city and low damping.177s A NEW INDUCTION AC LELFEA ioR

E Al N (1 20 MeV eiriginally called Rhro-tri Kerst. 1st 15th

Jan' 1042, \"l. or, No, 12. pp 93-94)

For previous work .set 3130 of turf and batlitreference for a discussion of the name

Betatron see .'',./e -me, 23rd Jan 1942.

\ tt'let17th, Sull)4: , V:d 411 N,4e.ealsi' '73sI.

t.


1779. ON THE THEORY OF THE ELECTRON -PLASMA

OSCILLATIONS.-Seeliger. (See 1685.)

1780. THE CONTACT CONVERTER [" K -Converter ,"for Rectification of Polyphase Current :with Mechanically Opened & Closed Con-tacts protected against Arcing by Deviceof D.C.-Polarised Iron -Cored Chokes : HighEfficiency].-Koppelmann. (E. T.Z., 2nd Jan.1941, Vol. 62, No. I, pp. 3-16 : Discussion

pp. 16-20.)1781. SELENIUM RECTIFIERS FOR CLOSELY REGU-

LATED VOLTAGES [particularly a Controlled -Output -Voltage Circuit using 'Regulating &Shunt Reactors].-Yarmack. (Elec. Com-munication, No. 2, VOL 20, 1941, pp. 124-131.)Some sections have already appeared else-where (see 247 of January). The papersupplements that of Clarke (825 of March).

1782. THE ELECTRON THEORY OF CRYSTALLINECOMPOUNDS OF THE TYPE OF COPPER OXIDE[Limitations of Present Theory : Energy ofInternal Ionisation : Other Possible Mechan-isms].-Dressnandt. (Sci. Abstracts, Sec. A,Dec. 1941, Vol. 44, No. 528, p. 399.)

1783. CONTRIBUTION ON THE SENSE OF RECTIFICA-TION IN SEMICONDUCTORS [Measurements onSintered Bodies made from CdO, TiO2 (bothof Reduction or " Surplus " Type), NiO(Oxidation or " Defect " Type), & CuO(Type still Contested), with View to FurtherConfirmation of Schottky's Rule of Polarity].-Klarmann. (Wiss. Veroff. a. d. Siemens -W erken, No. 2, VOL 18, 1939, pp. 78-83.)

1784. WEAR AND FRICTION IN SLIDING CONTACTS,PARTICULARLY BETWEEN CARBON BRUSHESAND COPPER RINGS [Influence of Pressure,Velocity, Moisture, & Current Strength :etc.].-Holm & others. (Wiss. Veroff. a. d.Siemens-Werken, No. 1, Vol. 18, 1939,pp. 73-100.) For later work see 86o ofMarch.

1785. NEW OBSERVATIONS ON SILVER CONTACTS[Cathode Contact " formed " by GradualIncrease of Current, so that Limiting Cur-rent is about Doubled].-Burstyn. (E.T.Z.,13th Feb. 1941, Vol. 62, No. 7, pp. 149-150.)

1786. THE INDUCTANCE OF A " SIEVE " CONTACT.-Stormer. (Wiss.. V eroff. a. d. Siemens-Werken,No. 2, VOL 18, 1939, pp. 45-53.)

" If two metal parts furnish an electrical connec-tion only through a very small surface of contact,such a contact presents to the current a resistancewhich Holm, in analogy to the resistance which asieve presents to a flow of water forced through it,calls a sieve ' resistance, the contact itself beingtermed a ' sieve ' contact. At such a contact thecurrent flow lines are strongly compressed at thepoint of contact, and for the use of contacts inh.f. technique it is therefore important to knowwhether, as a result, any appreciable inductancedoes or does not appear, since the design of a con-tact might in some cases depend on this."

The question is treated mathematically withcertain simplifying assumptions. The results,applied to a relay with perfectly clean silver con-*

281

tacts with a pressure of roo gms and certain likelydimensions, show' that at a frequency no higherthan about 32 kc/s the inductive resistance of thecontact is. already as great as its ohmic resistance.In practice, however, the contact is coated with somekind of extraneous film and its ohmic resistance isconsiderably greater than that of the clean contact,so that in general the contact inductance may beneglected, provided that the permeability j.L of thematerial is not too high.

1787. HIGH - CONDUCTIVITY BERYLLIUM - COBALT -COPPER ALLOY [Mallory 73 BerylliumCopper : for Current -Carrying Springs, etc.].-(Engineering, loth April 1942, Vol. 153,p. 287.)

1788. THERMOSTAT METAL [Bimetallic Sheet &Strip].-Hood. (A STIVI Bulletin, Jan. 1942,No. 114, pp. 11-14.)

1789. THE USE OF INFRA -RED LAMPS FOR HEATINGAND DRYING.-Haynes. (Bull. Assoc. suissedes Elec., 14th March 1941, Vol. 32, No. 5,p. 86.) Summary of a lecture based partlyon the paper dealt with in 1200 of 1941.

1790. A NOTE ON THE USE OF BAKING SHELLAC

VARNISHES FOR COATING GRAPHITE -ON -GLASS RESISTANCES IN THE LABORATORY[for D.C. Amplifiers, etc : Successful Com-parison with Glyptal Lacquer Coatings].--Bhattacharya. (Indian Journ. of Phys.,Feb. 1941, Vol. 15, Part I, pp. 59-62.)

FIXED RESISTANCES FOR RADIO PURPOSES[Summary of Methods of Manufacture ofComposition & Wire -Wound Vitreous -Enam-elled Resistances]. - Iyengar. (Electra -technics [Bangalore], Nov. 1941, No. 14,

PP. 50-53)1792. ON THE TEMPERATURE RISE OF SOLID INSU-

LATING MATERIALS AT ULTRA-HIGH FRE-QUENCIES [Method using Small Radial Sticksof Polystyrol Resin or Fused Silica, stuckto Surface with Waxes of Different MeltingPoints, as Indicators, Time of Collapse beingmeasured : Some Results at 94 Mc/s :Alternative Use of Colour -Changing Paints].-Okazaki & Otuka. (Electrotech. Journ.[Tokyo], Feb. 1941, Vol. 5, No. 2, pp. 37-38.)See also 1793, below.

1793. DISFIGUREMENT OF HARD RUBBER DUE TODIELECTRIC LOSS UNDER ULTRA -HIGH-FRE-QUENCY HIGH -VOLTAGE FIELDS [and Com-parison with Steatite, etc.].-Okazaki &Ohtsuka. (Electrotech. Journ. [Tokyo], Feb.1941, Vol. 5, No. 2, pp. 38-39.) See also1792, above.

1794. TEMPORARY PROTECTION FOR CABLE SPLICES

[Use of " CR " Tape, Tough VulcanisedRubber lined with Tacky UnvulcanisedRubber].-Pike. (Bell Lab. Record, Feb.1942, VOL 20, No. 6, ,pp. 159-162.) Cf. 1531of May.

SYNTHETIC RUBBER [Short Survey]. -Hayden. (Engineer, 3rd April 1942, Vol. 173,pp. 285-287.)

1791.

1795.


1796. THE PLASTIC FLOW FROM CENTRAL ORIFICESOF VARIOUS FORMS.-Unckel. (Zeitschr. f.tech. Phys., No. 1o, Vol. 22, 1941, pp. 245-248.) Extension to 837 of March.

1797. CRYSTALLINITY IN CELLULOSE ESTERS [X -RayDiffraction Studies of Plastics].-Baker.(Bell Lab. Record, Feb. 1942, Vol. 2o, No. 6,pp. 155-158.) See also 5507 of May.

1798. SILICONES [By -Products of Silicon/CarbonCompounds] AS HEAT -RESISTING INSULATINGRESINS.-(Sci. News Letter, 28th Feb. 1942,Vol. 41, No. 9, P. 143: paragraph only.)

1799. PLASTICS [including the New Polymers ofMethyl Silicone & Related Compounds].-,Carsley. (Electrician, 27th March 1942,Vol. 128, pp. 288-289.)

1800. A HIGH -FREQUENCY CERAMIC INSULATOR FITFOR MACHINING [Search for Insulator withLow Dielectric Loss, No Shrinkage by HeatTreatment, Suitable for Machining, Stableagainst Moisture & Chemicals : resultingin Development of " Teison No. 2 "].-Kobayashi & others. (Electrotech. Journ.[Tokyo], Feb. 1941, Vol. 5, No. 2, p. 40.)

1801. THE TITROMETRIC DETERMINATION OF THEPERMEABILITY TO WATER OF INSULATINGMATERIALS [in place of the Usual Gravi-metric Methods : Application to Styroflex,Benzyl-Cellulose, & Whale Oil (as Sub-stitute for Linseed Oil) : Equal Permeabili-ties for Vapour & Liquid : etc.].-Nagel &Brandenburger. (Wiss. Verbff. a. d. Siemens-Werken, No. 2, Vol. 18, 1939, pp. 97-504.)

1802. ON THE THERMAL CONDUCTIVITY OF DI-ELECTRICS.-Pomeranchuk. (Phys. Review,1st Dec. 1941, Vol. 6o, No. II, pp. 82o-821.)

1803. ON THE DISCHARGE LAG IN SOLID INSULATINGMATERIALS.-StTigel. (WiSS. Veroff. a. d.Siemens-Werken, No. 1, Vol. i8, 1939,pp. 101-119.)

Measurements, with the " time transformer "(see for example 1933 Abstracts, p. 225), on mater-ials of very diverse structures, such as glass, mica,Resistit (laminated mica/paper composition), press -board, and nitrocellulose, some in air and some ininsulating liquids. Among other results, it wasfound that solid insulating materials can be divided,as regards the potential dependence of their dis-charge delays, into two classes : for those withcrystal structure (mica) or crystalline structure(porcelain) the building -up time for breakdown waswell below 5µs when the surge ratio (i.e. ratio ofsurge potential to static a.c. breakdown potential)was only 1.2, whereas for fibre -containing materialssuch short times were only reached for surge ratiosover 2.0.

1804. NOTE ON MECHANISM OF THE ELECTRICALBREAKDOWN IN IONIC CRYSTALS [SuggestedExplanation of Failure of Frohlich's Theory(based on von Hippel's Picture) at HighTemperatures].-Suita. (Electrotech. Journ.[Tokyo], March 1941, Vol. 5, No. 3, p. 6o.)

June, 1942

1805. THE BREAKDOWN STRENGTH OF MIXTURES OFDIELECTRIC LIQUIDS [Hexane/H0ptane, Hep-tane/Xylol, Heptane/Nitrobenzol, etc.].-Ruhle. (Arch. f. Elektrot., 30th Sept. 1941,Vol. 35, No. 8, _pp. 490-505.)

" It is of great _theoretical and practical interestto learn the_behaviour of liquid insulating materialsconsisting of several components. For theory, theinformation may bring a new contribution to ourunderstanding of the breakdown mechanism.Practically, such investigations are important forthe use of mixtures of various mineral oils and forthe preparation of synthetic insulating oils." Thetests were all at 5o c/s. Among the results, it wasfound in most cases that the breakdown voltagewas independent of the concentration of the mix-tures, so long as the components had equal break-down strengths ; but that if one had a lowerstrength, a quite small percentage of it produced alarge decrease in the breakdown voltage : increasingthe percentage, had little or no further effect. Aspecial behaviour was shown by the halogen de-rivatives of the aromatic hydrocarbons : theaddition of a small percentage led to a raising ofthe breakdown voltage by 3o-40%. Increasing thepercentage beyond a certain point produced a largedrop. The position and width of the maximumdiffered with different kinds of added substance :chlorbenzol gave a particularly broad maximumand seems therefore particularly suitable for suchuse (Fig. 6).

1806. THE MIXED -BODY PROBLEM IN CONDENSERTECHNIQUE. - Buchner (with Zauscher).(Wiss. Veroff. a. d. Siemens-Werken, No. 2,Vol. 18, 5939, pp. 84-96.)

In applying the " mixture " formulae to the pro-blems of practical condenser design, the importantpoints are not merely the synthesis of the dielectricconstant of the mixed body from those of its com-ponents but also the question of the influence onit of the always present losses and the dependenceof the mixed -body losses on the individual lossesof the components. Of particular value is theequation obtained by Lichtenecker & Rother,EA: = 81,1k + 82E21', which has worked well in manycases : here k is a constant dependent on the formand distribution of the components but not on theratios of their amounts, and 8, and 52 are the" volume shares " of the components : k may haveany value between + 5 and - 1. For k = f thisformula becomes that for the parallel connectionof the two components, E = 8,e1 + 8,e,, whilefor k = -1 it becomes that for the series connection,1/E = 8,/e, 81/e, ; for k = o it becomes theLichtenecker logarithmic mixing rule, log E =-8, log e, + 82 log e2. All these formulae can beextended directly to any number of components,so that finally a formula is obtained for a mixed

body of n components, e = E 8i eik. This eqn. 5,

like the others, is based on the implicit assumptionthat no energy is lost in the individual components :the complex dielectric constant of a dielectricpossessing losses is given by eqn. 6, and the introduc-tion of this into eqn. 5 yields eqn. 8 for the resultantloss factor of a multi -component body (simplifying


to approximate formulae eqns. g & 10 under certainconditions) and eqn. II for its dielectric constant.For the special case when k = o (logarithmicmixing rule) the equations are given at the end ofsection I.

Section 2 deals with the range of applicability ofthe basic Lichtenecker-Rother formula, the work ofBruggeman (2424 of 1936 and 1087 of 1937) beingdiscussed here. An important application is toporphyrous mixed bodies, and section 3 begins byconsidering those bodies in which Rutile is addedto obtain high dielectric constants (Fig. 3) : thelogarithmic mixing rule gives a good approximationhere. The most important condenser type is theimpregnated paper condenser and the questionarises as to which mixing formula best representsthe paper structure : a comparison between the"two-dimensional lamellar ' and " two-dimen-sional cylindrical " formulae of Bruggeman, theabove - discussed logarithmic rule, Rayleigh'scylinder formula, and the " series connection "formula mentioned above (case k = - 1), showsthat the last gives results both for the di-electric constant and dielectric losses which agreebest with measured values. The reason for thegood results given by this simple two -layer seriesformula over such wide ranges of paper and im-pregnating material is examined, and finally theinfluence of the oil or air -filled space betweendielectric and metal coating in condensers isdiscussed.

1807. REMARKS ON MY PAPER " MODERN CON-DENSERS FOR COMMUNICATION ENGINEERINGAND THEIR DEVELOPMENT " [Addition ofData for " Tempa S," and the Possibility,afforded by Ceramic Condensers only, ofbuilding Condensers with Any DesiredTemperature Coefficient between 120 and- 700 x Io-6/°C : Suitable Parallel or SeriesConnection gives Any Coefficient within

ro x io-6/°C]. - Linder. (E.T.Z., 6thFeb. 1941, Vol. 62, No. 6, p. 142.) See 555of 1941.

1808. PERMEABILITY, INDUCTANCE, AND HYSTERE-SIS RESISTANCE FOR SINUSOIDAL FIELDSTRENGTH AND FOR SINUSOIDAL INDUCTION.-Miicke. (See 1759.)

1809. MAGNETIC MATERIALS FOR TRANSFORMERS,PARTICULARLY INSTRUMENT TRANSFORMERS[with Curves of Hyperms I to 5 : Hyperm 20for H.F. Technique, with Permeabilityscarcely decreasing with Increasing Fre-quency, & High Specific Resistance keepingdown the Eddy -Current Losses at VeryHigh Frequencies].-Meyer & Fahlenbrach.(E.T.Z., 2nd Jan. 1941, Vol. 62, No. I,p. 21 : summary, from Tech. Mitt. Krupp.)

STATIONS, DESIGN AND OPERATION

1810. AUTOMATIC RADIO RELAY SYSTEMS FORFREQUENCIES ABOVE 500 MEGACYCLES.-Smith. (See 1725.)

1811. A SHORT-WAVE RADIO -TELEPHONE TRANS-MITTER AND RECEIVER BUILT LIKE LARGE-SCALE " FRENCH " HANDSET [held to Mouth

283

& Ear : Weight 4 lb : Range about I Mile].-(Sci. News Letter, 28th Feb. 1942, Vol. 41,No. 9, p. 143: paragraph only.)

1812. A LOW -POWER INSTALLATION FOR ULTRA-HIGH -FREQUENCY RADIO -TELEPHONE LINKS[5 -Watt Transmitter combined with 6 -ValveSuperheterodyne Receiver, for Duplex Opera-tion at Fixed Frequency in 30-45 Mc/s Band :Single Crystal controls both Transmitter &Receiver : Simple Bell -Calling System].-Honnor & Trew. (A.W .A. Tech. Review,Dec. 1941, Vol. 5, No. 6, pp. 287-294.)

1813. THE POLICE WIRELESS SYSTEM OF THE TOWNOF ZURICH [Use of Frequency Modulation :Remote -Control U.S.W. Receivers mountedon Top of Serious Obstacles : etc.].-Wertli.(Bull. Assoc. suisse des Elec., 19th Dec. 1941,Vol. 32, No. 25, pp. 711-717 : in. German.)

1814. DESIGN CONSIDERATIONS OF ULTRA -HIGH -FREQUENCY AIRCRAFT EQUIPMENT.-Gard-ner. (Proc. I.R.E., NOV. 1941, Vol. 29,No. I1, p. 605: summary only.) From theWilcox Electric Company.

1815. THE USE OF RADIO IN MODERN AIR TRANS-PORTS.-Knox. (Proc. I.R.E., Nov. 1941,Vol. 29, No. II, p. 605: summary only.)From Northwest Airlines.

1816. A NEW MARINE RADIO, UNIT FOR CARGOVESSELS [prompted by U.S.A. Programmeof Mass Production of Merchant Vessels].-Girard. (Elec. Communication, No. 2, Vol.20, 1941, pp. 71-72.)

1817. MODERN MARINE COMMUNICATION EQUIPMENT[including the America's Installation : theUse of Inductance Tuning: etc.].-McDonald.(Proc. I.R.E., NOV. 1941, Vol. 29, No. II,p. 6o5 : summary only.) From the Radio -marine Corporation.

1818. THE MODULATION AND DEMODULATIONMETHOD USING THE CONDENSERS OF PERIODI-CALLY VARYING CAPACITY [With Applicationsto Remote Measurement & Secret Communi-cation : Analysis].-Tomituka. (Electrot.Journ. [Tokyo], March 1941, Vol. 5, No. 3,PP. 43-44.)

1819. DIPLEX [Transradio International Systemgiving Two Messages in One Direction byTransmitter with Output commutated fromOne Frequency to Another at a Rhythmsuperior to Keying Rhythm].-Noizeux,Krahenbiihl, & Noviks. (Proc. I.R.E.,Dec. 1941, Vol. 29, No. 12, pp. 609-613.)Cf. Gracie's independent paper, 693 of 1938.

1820. SOME ASPECTS OF THE PROBLEM OF THEUTILISATION OF THE RADIOELECTRIC FRE-QUENCIES [including Future Possibilities :Doubtful Desirability of American " Chan-nel " System for Europe : etc.].-Corbaz.(Bull. Assoc. suisse des Elec., 29th Aug.1941, Vol. 32, No. 17, pp. 411-416: inFrench.) Concluded from No. 16.


GENERAL PHYSICAL ARTICLES

1821. " JTDISCHE UND DEUTSCHE PHYSIK "[" Jewish & German Physics " : ExtremelyCritical Book Review].-Muller & others.(Zeitschr. f. tech. Phys., No. 1, Vol. 23, 1942,p. 25.)

1822. THE PHYSICAL INTERPRETATION OF QUANTUMMECHANICS [Bakerian Lecture]. - Dirac.(Proc. Roy. Soc., Ser. A, 18th March 1942,Vol. ,8o, No. 98o, pp. 1-4o.)

1823. THERMODYNAMIC FUNCTIONS FOR TWO-DIMENSIONAL QUANTUM STATISTICS [With

Application to Deduction ' of MagneticSusceptibility of Free Electron Gas whenElectrons are confined to a Plane].-Singb.(Indian Journ. of Phys., Feb. 1941, Vol. 15,Part I, p. 73-78.) For the application see557 of February.

1824. A GENERAL THEOREM ON THE INITIALCURVATURE OF DYNAMICAL TRAJECTORIES.-Kasner & Mittleman. (Proc. Nat. Acad.Sci., Feb. 1942, Vol. 28, No. 2, pp. 48-72.)

" If a particle starts from ' maximum rest ' inan acceleration field of order n, the initial curvatureof the trajectory is n ! (n - 1)! /(2n - 1)! times thecurvature of the line of force through the initialposition."

MISCELLANEOUS

1825. ELLIPTIC AND SPHEROIDAL WAVE FUNC-TIONS.-Chu& Stratton. (See 1594.)

1826. LAPLACE TRANSFORMATION AND OPERATIONALCALCULUS, and A BASIS FOR THE COMPLEXCALCULATION OF ALTERNATING - CURRENTPROBLEMS.-Wagner : Landolt. (See 1637& 1638.)

1827. ON THE REPRESENTATION OF AN EXPERI-MENTAL FUNCTION BY A RATIONAL FRAC-TioN.-Vernotte. (Comptes Rendus [Paris],29th Sept. 1941, Vol. 213, No. 13, Pp. 433-435.)

1828. A METHOD OF SUCCESSIVE APPROXIMATIONSOF EVALUATING THE REAL AND COMPLEXROOTS OF CUBIC AND HIGHER -ORDER EQUA-TIONS, and A COMPARISON OF METHODS FOREVALUATING THE COMPLEX ROOTS OFQUARTIC EQUATIONS [in Study of DampedVibrations].-Lin : Sharp. (Journ. of Math.& Phys. [of M.I.T.], Aug. 1941, Vol. 20,No. 3, pp. 231-242 : pp. 243-258.)

1829. ON A CLASS OF SINGULAR INTEGRAL EQUA-TIONS [Solution of Equation

f (x) = h(x)-{-Jk (x - y)f(y)dy (o < x < co )1 .

-Reissner. (Journ. of Math. & Phys. [ofM.I.T.], Aug. 1941, VOL 20, NO. 3, pp. 219-223.)

183o. A LEAST -SQUARE PROCEDURE FOR SOLVINGINTEGRAL EQUATIONS BY POLYNOMIALAPPROXIMATION [Improved Technique givingMuch Greater Accuracy].-Hildebrand &Crout. (Journ. of Math. & Phys. [of M.I.T.],Aug. 1941, Vol. 20, No. 3, pp. 310-335.)Illustrated by application to charge -distri-bution problems : for the previous paper see167o of 1940.

June, 1942

1831. THE CINEMA INTEGRAPH IN INTERREFLEC-TION PROBLEMS [Multiple Reflection ofRadiant Energy between Reflecting Surfacesor between Parts of Same Surface : Use ofCinema Integraph (4107 of 1940) for Numeri-cal Solution of Buckley's Integral Equation].-Hedeman. (Journ. of Math. & Phys. [ofM.I.T.], Dec. 1941, Vol. 20, pp. 402-417.)

1832 MATHEMATICAL THEORY OF THE DIFFEREN-TIAL ANALYSER.-Shannon. (Journ. ofMath. & Phys. [of M.I.T.], Dec. 1941, Vol.20, No. 4, pp. 337-354.)

1833. " SIX -PLACE TABLES " [Book Review].-Allen. (Proc. I.R.E., Nov. 1941, Vol. 29,No. I1, pp. 606-607.)

1834. THE DISTRIBUTION OF A PRODUCT FROMSEVERAL SOURCES TO NUMEROUS LOCALI-TIES [Calculation of Least Costly Manner ofDistribution from Several Factories].-Hitchcock. (Journ. of Math & Phys. [ofM.I.T.], Aug. 1941, Vol. 20, pp. 224-230.)

1835. JOINT MEETING TO DISCUSS THE APPLICATIONOF STATISTICAL CONTROL OF THE QUALITYOF MATERIALS AND MANUFACTURED PRO-DUCTS.-Darwin : Gill. (Engineer, 27thMarch 1942, Vol. 173, pp. 266-267.) For along report see Electrician, 24th April 1942,Vol. 128, pp. 388-393 : also Editorial, pp.383-384.

1836. QUALITY CONTROL IN MANUFACTURE.-Ris-sik. (Electrician, 27th March 1942, Vol. 128,pp. 276-280.)

See also Times leader, 16th April 1942. Forprevious work see, for example, Shewhart, 1930Abstracts, p. 527 (r -h column) ; 1933 Abstracts,p. 519 (1-h column) ; 3647 of 1940 ; and 1837,below, which also gives important references :Rissik, 625 of 1941, 297 of January, and 1565 ofMay : Dudding & Jennett, O'Dea, 3646 of 1940:Peters & van Voorhis, Simon, 1194/5 of April.

1837. CONTRIBUTION OF STATISTICS TO THE SCIENCEOF ENGINEERING : A SURVEY OF THE POTEN-TIAL CONTRIBUTIONS OF STATISTICS TO THESCIENCE OF ENGINEERING AS A NATIONALAssEL-Shewhart. (Bell Tel. S. Tech. Pub.,Monograph B-1319, 28 pp.)

1838. A NEW HIGH -SENSITIVITY SYSTEM OF FAC-TORY CONTROL OF RAW MATERIAL BYMEASURING THE MAGNETIC PERMEABILITY .-Yanus & others. (Journ. of Tech. Phys. [inRussian], No. Io, Vol. I1, 1941, pp. 936-946.)

The theory and practical applications are dis-cussed of a method in which the material is pulledthrough a magnetising coil (or between two coils inthe case of sheet material) and the magnetic fluxin the material observed with the aid of anothercoil. It is shown that a much higher sensitivity isobtained with an open magnetic circuit, i.e. withoutthe yoke over the magnetising coil.1839. CORRECTION TO " DETERMINATION OF THE

STATIC AND DYNAMIC CONSTANTS BY MEANSOF RESPONSE CURVES ".-Bernhard. (Journ.Applied Phys., Feb. 1942, Vol. 13, No. 2,p. 116.) See 905 of March.

J


PANORAMIC X-RAY EQUIPMENT [All Pointsof View combined in One Exposure : Ring -Shaped Source].-Schiebold. (Sci. NewsLetter, 24th Jan. 1942, VOL 41, No. 4, p. 57.)Note on a German patent : particularly forcrystal structure, etc. See also note inIndustrial & Engineering -Chemistry (NewsEdition), loth Dec. 1941, Vol. 19, No. 23,p. 1408.

1841. OUTPUT OF AN X-RAY TUBE IN RELATIONTO A HIGH -VOLTAGE MULTIPLYING SCHEME,and ON X-RAYING OF COMMERCIAL GOODSAND DETECTION OF INTERIOR DEFECTS OFDIFFERENT DENSITY.-Revutzkaja & Akat-nova : Tra,peznikov. (Journ. of Tech. Phys.[in Russian], No. 3, Vol. II, 1941, pp. 254-258 : pp. 259-265.)

THE DETERMINATION OF THE THICKNESSOF ELECTROLYTIC COATINGS : PART 2 .-Gepshteyn [Gepstein] & others. (Journ.of Tech. Phys. [in Russian], No. 6, Vol. II,1941, pp. 525-531.)

An experimental verification of a method pro-posed by Palatnik (ibid., Vol. 1o, 1940, p. 1975) inwhich use is made of X-ray spectrograms. Nickeland tin coatings of thickness between o. i andro IL were measured.

1843. SOME ASPECTS OF THE IMPACT OF WAR. ECONOMY ON CIVILIAN RADIO [Symposium].-Hoyle & others. (Proc. I.R.E., Nov. 1941,Vol. 29, No. II, p. 603 : summaries only.)

1844. A.R.P. IN THE ELECTRICAL INDUSTRY .-Brierly. (BEA MA Journal, Jan., Feb., &March 1942, Vol. 49, Nos. 55/57.)

1845. OBITUARY : SIR W. H. BRAGG, 0.M., K.B.E.,F.R.S.-(Engineering, loth March 1942,Vol. 153, pp. 234-236 : Nature, 28th March1942, Vol. 149, pp. 346-351.)

1846. PEDER OLUF PEDERSEN : I 874-1941 .-(Elec. Communication, No. 2, Vol. 20, 1941,pp 133-135.)

1847. " INGENIEURE " [Discussions on the Sig-nificance, Vocation, & Position of Engineers :Book Review].-Munzinger. (E.T.Z., 12thFeb. 1942, Vol. 63, No. 5/6, pp. 78-79.)An enthusiastic review.

1848. DISCUSSION ON " A CRITICAL REVIEW OFEDUCATION AND TRAINING FOR ENGINEERS."-Fleming. (Electrician, 27th March 1942,Vol. 128, pp. 280-282.) See also Nature,2nd May 1942, pp. 482-483.

1849. PHYSICISTS AFTER THE WAR [Summary ofRoyal Institution Lecture].-Bragg. (Engi-neering, 3rd April 1942, pp. 272-273.)

" Real advance demands constant contact withother people and outside ideas. No man wakes upin the morning and says, ' I'll have a bright ideato -day.' Bright ideas result from the clash ofintellects : they have two parents."1850. THE COMPARATIVE COST OF LOAN SERVICE

AND OF MICROFILM COPYING IN LIBRARIES.-Seidel'. (Science, 28th Nov. 1941, Vol. 94,pp. 515-516.)

1840.

1842.

285

1851. RADIO PROGRESS DURING 1941 : ELEC-TRONICS, RADIO TRANSMITTERS AND TRANS-MITTING ANTENNAS, RADIO RECEIVERS,FREQUENCY MODULATION, TELEVISION &FACSIMILE, PROPAGATION, PIEZOELECTRI-CITY, ELECTROACOUSTICS. (PY0C. I.R.E.,Feb. 1942, Vol. 30, No. 2, pp. 57-71.)

1852. " QUESTIONS AND ANSWERS IN ELECTRICALENGINEERING PRACTICE," and " QUESTIONSAND ANSWERS IN RADIO -COMMUNICATION "[Book Reviews].-Dharap. (Electrotechnics[Bangalore], Nov. 1941, No. 14, p. 65 : p. 65.)The questions were set in examinations heldby the City & Guilds of London Institute.

1853. " RADIO AT ULTRA -HIGH FREQUENCIES :PART I " [Transmitting, Propagation &Relaying, Measurements, Reception : etc :Book Review].-RCA Institutes TechnicalPress. (Proc. I.R.E., NOV. 194r; Vol. 29,No. II, p. 607.)

1854. INFLUENCE OF THE WAVE -SOURCE AREA ONTHE AMPLITUDE OF SOIL VIBRATIONS, andTHE CHOICE OF THE DEPTH OF THE SOURCEAND RECEIVER OF WAVES PROPAGATING INTIE Son..-Barkan. (Journ. of Tech. Phys.[in Russian], No. Ii, Vol. u, 1941, pp. 1014-1019 :, pp. I020-1028.)

1855. A METHOD OF MINIMISING SUPERCOOLING,AND ITS APPLICATION IN THE DETERMINATIONOF FREEZING POINTS [of Soils, etc.] FROMDIELECTRIC - CONSTANT MEASUREMENTS. -Shaw. (Review Scient. Instr., Jan. 1942,Vol. 13, No. r, pp. 2-5.)

1856. AN INVESTIGATION OF THE PROPERTIES ANDAPPLICATIONS OF THE GEIGER - MULLERPHOTOELECTRON COUNTER [Nickel Type:Sensitivity estimated as Comparable withThat of Eye, Less than That of Liquid -Air -Cooled Electron Multiplier (75o Quanta perSecond compared with 4), Comparable(although Action is Non -Accumulative) toPhotographic Plate : Other Counters].-Duffendack & Morris. (Journ. Opt. Soc. Am.,Jan. 1942, Vol. 32, No. 1, pp. 8-24.)

1857. AN ARRANGEMENT FOR THE GEIGER -COUNTERSTUDY OF WEAK RADIOACTIVITIES [Sensi-tivity more than Doubled by Elimination ofResponses to Cosmic Radiation].-Berthelot.(Comptes Rendus [Paris], 23rd June 1941,Vol. 212, No. 25, pp. 1087-1090.)

1858. HELIUM -FILLED GEIGER-MULLER COUNTERS[Best Plateau & Lowest Threshold given byHelium/Methyl-Alcohol].-Kapur & others.(Current Science [Bangalore], Dec. 1941,Vol. 10, No. 12, pp. 521-522.)

1859. DIRECTIONAL PROPERTIES OF SELF -QUENCH-ING COUNTERS [Stever's " Small -Bead -onWire " Method : " Segmented Counter "Method], and THE DISCHARGE MECHANISMOF FAST G -M COUNTERS FROM THE DEADTIMEEXPERIMENT.-Ramsey : Stever. (Phys.Review, 1st/15th Jan. 1942, Vol. 61, No. 1/2,pp. 90-97 : pp. 38-52.)


1860. THE " ULTRA " INCENDIARY BOMB DE- 1868.TECTOR.-Ultra Electric. (Electronic Eng:g,Aug. 1941, Vol. 14, No. 162, p. 339.) Fora test report see September issue, p. 424.

1861. EXACT CONTROL OF A LUMINOUS FLUX,HOWEVER WEAK, BY THE USE OF TWOVACUUM PHOTOCELLS IN SERIES [particularlyBoutry-Type Cells requiring only 8 Voltsand having Very Low Dark Current].-Fleury. (Comptes Rendus [Paris], 5th May1941, Vol. 212, No. 18, pp. 753-755.)

This arrangement, quite different from theordinary differential photocell combination, hasthe anode of one cell connected directly to thephotocathode of the other. Using Boutry-typecells (3305 bis of 1938) a variation of 1% in amillilumen gave a voltage change of about 1 volt,easily measured within 2% by a Lindemann electro-meter.1862. KNORR - ALBERS MICROPHOTOMETER [for

Analysis of Spectrographic Plates or Films :with Scanning Unit & " Speedomax "Recording Unit (Pen-and-Ink)].-Leeds &Northrup Company. (Review Scient. Instr.,Jan. 1942, Vol. 13, No. 1, pp. 38-39.)

1863. DISCUSSION ON " A ROTATING DIFFERENTIALPHOTOELECTRIC PHOTOMETER FOR PRE-CISION WORK." - MacGregor - Morris &Stainsby. (Proc. Phys. Soc., 1st Jan. 1942,Vol. 54, Part r, No. 301, pp. 66-69.) See318 of January.

1864. SPEKKER PHOTOELECTRIC FLUORIMETER [forChemical & Biochemical Analysis, etc.].-(Review Scient. Instr., Nov. 1941, Vol. 12,No. II, p. 558.)

1865. A QUARTZ PHOTOELECTRIC SPECTROPHOTO-METER [using RCA Type 919 Phototube andSpecial RCA C7o32 Tube with Great Sensi-tivity below 625 mµ].-Cary & Beckman.(Journ. opt. Soc. Am., Nov. 1941, Vol. 31,No. II, pp. 682-689.)

1866. A RECORDING SPECTROPHOTOMETER ANDSPECTROPOLARIMETER [Completely Auto-matic, Wide Spectral Range].- BrodeJones. (Journ. Opt. Soc. Am., Dec. 1941,Vol. 31, No. 12, pp. 743-749.)

1867. ON THE MEASUREMENT OF THE ABSORPTIONCOEFFICIENTS OF GASES IN THE EXTREMEULTRA -VIOLET REGION OF THE SPECTRUM[Comparison of Direct (Photoelectric Photo-metry) & Indirect (Photographic Blackening)Methods].-Matare. (Zeitschr. f. tech. Phys.,No. Io, Vol. 22, 1941, pp. 260-268.)

Particular attention is paid to the details of thedirect method, including preliminary tests to obtaina satisfactory photocell/amplifier/meter connection(a particularly sensitive arrangement was with aquadrant electrometer in the anode circuit, Fig. 7 :this would be particularly suitable for stellar photo-metry) : and to obtain a cell sufficiently sensitivein the region below zoo mil (a sodium ultra -violetcell, Pressler type, with a thin layer of calciumtungstate on its front glass wall to serve as a fre-quency converter, was found to give an improvedoutput). Many literature references are given.

June, 1942

PHOTOELECTRIC SMOKE -METERS [Survey, withLiterature & Patent References : Projector& Receiver Design : Prevention of Deposi-tion of Foreign Matter on Windows : VoltageRegulation : Balanced Systems :Wey. (Engineer, 3rd, loth, & 17th April1942, Vol. ' 173, pp. 283-285, 300-303, &320-322 : to be contd.)

1869. A SELENIUM PHOTOCELL FOR LIGHT MEASURE-MENTS.-PutseykO. (See 1739.)

1870. A METHOD OF LIGHT MODULATION BASED ONTHE USE OF A QUARTZ CRYSTAL AT HIGHVOLTAGES.-Mandelstam & others. (Men-tioned in 1755, above.)

1871. TROPICAL CLIMATE AND COMMUNICATIONTECHNIQUE.-Schulze. (See 1672.)

1872. AN INTEGRATING ALTIMETER [ElaboratedAneroid Barometer automatically integratingthe Altitude/Pressure Equation (eliminatingUncertainty of Height/Temperature Assump-tions) and giving Record of the Ascent].-Charron. (Comptes Rendus [Paris], 19thMay 1941, Vol. 212, No. 20, pp. 852-854.)

1873. ELECTRONIC MEASUREMENTS IN AIRCRAFT -ENGINE MANUFACTURE.-Whitmore. (Proc.I.R.E., Nov. 1941, Vol. 29, No. 11, p. 605 :summary only.) From the General MotorsCorporation.

1874. ELECTRICAL [Capacitance -Change] INDICATORFOR INTERNAL - COMBUSTION ENGINES.-Hagendoorn & Reynst. (Zeitschr. V.D.I.,loth Jan. 1942, Vol. 86, No. 1/2, p. z2:summary, from Philips Tech. Rundschau,Vol. 5, 1940, p. 356 onwards.) The capa-citance is only 1.5 µµ.F, the gap 0.2 mm, thenatural frequency of the membrane 25 kc/s.

1875. THE MEASUREMENT OF SMALL CURRENTS ANDVOLTAGES, AND SMALL CHANGES IN LENGTH,WITH THE - BOLOMETRIC COMPENSATOR.-Merz & Niepel. (See 1746.)

1876. THE DYNETRIC BALANCING MACHINE [Out-puts from Velocity -Type Pick -Ups, at EachBearing, fed into Network separating Effectsof Unbalance in Each Plane : AngularPosition of Unbalance also shown].-yore.(Proc. I.R.E., Dec. 1941, Vol. 29, No. 12,pp. 666-667: summary only.)

1877. A NEW PRINCIPLE FOR STABLE D.C. AMPLI-FICATION [for Process Control & OtherPurposes].-Eberhardt & others. (See 1633,)

1878. THE APPLICATION OF THE CATHODE-RAYOSCILLOGRAPH TO THE MEASUREMENT OFTHE INCLINATION VECTOR [for Remote Indi-cation] .-Goncharski. (See 1772.)

1879. THE ELECTRICAL CAPACITANCE DIAPHRAGMMANOMETER [for Direct Measurements inArterial Blood Stream, and Other Purposes :with Crystal -Controlled R.F. Oscillator &Cathode -Ray Tube Indicator/Recorder).-Lilly. (Review. Scient. Instr., Jan. 1942,Vol. 13, No. 1, pp. 34-37.)

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